2. Symbolism and complex technology in the deep past

First, it is useful to briefly review the archaeological record. Evidence for technological complexity in the human lineage has a deep history. Hafted and other multicomponent tools, often seen as a stage-post in human evolution (Barham, Reference Barham2013; Sykes, Reference Sykes, Coward, Hosfield, Pope and Wenban-Smith2015; Wadley, Hodgskiss, & Grant, Reference Wadley, Hodgskiss and Grant2009), have multiple centres of origin (Blinkhorn, Reference Blinkhorn2019) dating to perhaps 500 ka and at least 280 ka in Africa (Sahle et al., Reference Sahle, Hutchings, Braun, Sealy, Morgan, Negash and Atnafu2013; Wilkins, Schoville, Brown, & Chazan, Reference Wilkins, Schoville, Brown and Chazan2012) and at least 300 ka in South Asia (Blinkhorn, Reference Blinkhorn2019). Unhafted projectile weapons have an even deeper history, dating to perhaps 2 million years based on Homo erectus shoulder morphology (Roach & Richmond, Reference Roach and Richmond2015) and at least 500 ka (Roberts, Reference Roberts1998; Thieme, Reference Thieme1997). The production of pitch tar adhesive, perhaps by distillation, has been identified in Neanderthal contexts (Sykes, Reference Sykes, Coward, Hosfield, Pope and Wenban-Smith2015; but see Schmidt et al., Reference Schmidt, Blessing, Rageot, Iovita, Pfleging, Nickel and Tennie2019) dating to 200 ka. The use of charcoal in bedding, potentially as insect repellent (Wadley et al., Reference Wadley, Esteban, De La Peña, Wojcieszak, Stratford, Lennox and Sievers2020), dates to 200 ka. The heat treatment of raw materials in tool manufacture dates to perhaps 164 ka (Murray, Harris, Oestmo, Martin, & Marean, Reference Murray, Harris, Oestmo, Martin and Marean2020). Moreover, the creation of wooden structures with joinery dates to 476,000 ka (Barham et al., Reference Barham, Duller, Candy, Scott, Cartwright, Peterson and Nkombwe2023).

Plausible evidence of “symbolic behaviour” also has a deep history. Evidence for ochre pigment processing, seen by some as indicative of ritual (e.g., Barham, Reference Barham2016) or symbolic thought (but see Mithen, Reference Mithen, Akazawa, Ogihara, Tanabe and Terashima2014) occurs in Neanderthal contexts, dating to at least 200–250 ka (Roebroeks et al., Reference Roebroeks, Sier, Nielsen, De Loecker, Parés, Arps and Mücher2012). Evidence for ochre use among Homo sapiens or direct ancestors dates to as early as 295 ka in Kenya (Brooks et al., Reference Brooks, Yellen, Potts, Behrensmeyer, Deino, Leslie and Clark2018) and 260 ka in Zambia (Barham, Reference Barham2002). Evidence of pigment use and transport dates back even earlier, for example, perhaps 500–300 ka in South Africa (Watts et al., Reference Watts, Chazan and Wilkins2016) although its ritual function is contentious (Barham, Reference Barham2016). Perforated shell beads appeared in North Africa at least 142 ka (Sehasseh et al., Reference Sehasseh, Fernandez, Kuhn, Stiner, Mentzer, Colarossi and Longet2021), the Levant by 120 ka (Mayer et al., Reference Mayer, Groman-Yaroslavski, Bar-Yosef, Hershkovitz, Kampen-Hasday, Vandermeersch and Weinstein-Evro2020), and by 70–80 ka in southern Africa (d'Errico & Backwell, Reference d'Errico and Backwell2016; Vanhaeren, Wadley, & d'Errico, Reference Vanhaeren, Wadley and d'Errico2019). Nonperforated shells from Israel also with a proposed symbolic function date to between 240 and 160 ka (Mayer et al., Reference Mayer, Groman-Yaroslavski, Bar-Yosef, Hershkovitz, Kampen-Hasday, Vandermeersch and Weinstein-Evro2020). Moreover, one temporally isolated carved mussel shell was found in H. erectus contexts from ~540–440 ka in Java, Indonesia (Dubois, Reference Dubois1908; Joordens et al., Reference Joordens, D'Errico, Wesselingh, Munro, De Vos, Wallinga and Roebroeks2015). The collection and transport of manuports – unmodified materials, with no clear utility – has also been highlighted as potentially indicating ritual behaviour (Wilkins et al., Reference Wilkins, Schoville, Pickering, Gliganic, Collins, Brown and Hatton2021). Stone manuports are ancient, appearing in Oldowan contexts (Dart, Reference Dart1974; Granger et al., Reference Granger, Gibbon, Kuman, Clarke, Bruxelles and Caffee2015) >2 Ma. The collection of crystalline manuports dates to 105 ka (Wilkins et al., Reference Wilkins, Schoville, Pickering, Gliganic, Collins, Brown and Hatton2021) in South Africa, whereas the collection of nonfood seashells dates to at least 90 ka in South Africa (Marean, Reference Marean2010) and the Levant (Bar-Yosef Mayer, Vandermeersch, & Bar-Yosef, Reference Bar-Yosef Mayer, Vandermeersch and Bar-Yosef2009).

Although complex and symbolic artefacts exist from great time depths (Barham et al., Reference Barham, Duller, Candy, Scott, Cartwright, Peterson and Nkombwe2023; Joordens et al., Reference Joordens, D'Errico, Wesselingh, Munro, De Vos, Wallinga and Roebroeks2015; McBrearty & Brooks, Reference McBrearty and Brooks2000), many scholars contend that 70–50 ka was yet characterised by rapid transformation, innovation, and change in the artefactual record (Kelly et al., Reference Kelly, Mackie and Kandel2023). From 50 ka and beyond, there are numerous examples of “indisputable art and personal ornaments” (Klein, Reference Klein2017, p. 204), including carved ivory figures such as the German Hohle Fels Venus (35 ka; Conard, Reference Conard2009) and Hohlenstein-Stadel lion-man (32–30 ka; Hahn, Reference Hahn1986; Wynn et al., Reference Wynn, Coolidge and Bright2009). The earliest examples of representational art come from Sulawesi, Indonesia, including depictions of hunting scenes in Sipong Cave (43.9 ka; Aubert et al., Reference Aubert, Lebe, Oktaviana, Tang, Burhan, Hamrullah and Brumm2019) and depictions of wild pigs from Leang Tedongnge cave (45.5 ka; Brumm et al., Reference Brumm, Oktaviana, Burhan, Hakim, Lebe, Zhao and Aubert2021). Examples of possible figurative art exist from potentially greater time depths, including dot art and hand stencils from northern Spain (Hoffmann et al., Reference Hoffmann, Standish, García-Diez, Pettitt, Milton, Zilhão and Pike2018). These date to perhaps earlier than 64.8 ka, which would associate them with Neanderthals (Hoffmann et al., Reference Hoffmann, Standish, García-Diez, Pettitt, Milton, Zilhão and Pike2018), although their age and provenance remain disputed (see White et al., Reference White, Bosinski, Bourrillon, Clottes, Conkey, Rodriguez and Willis2020). Many argue that the appearance of polished ostrich eggshell beads in Africa (see d'Errico et al., Reference d'Errico, Pitarch Martí, Shipton, Le Vraux, Ndiema, Goldstein and Boivin2020) and China (Wei et al., Reference Wei, d'Errico, Vanhaeren, Peng, Chen and Gao2017) during the same timeframe represents a similarly profound transformation (e.g., Klein, Reference Klein2017).

In addition to establishing and updating material chronologies, many have looked at this record to address broader questions about past minds, brains, and the cognitive evolution of our lineage.

3. Linking material culture to cognition, language, and behaviour

The profusion of symbolic evidence, especially after 70 ka (see Kelly et al., Reference Kelly, Mackie and Kandel2023), has led many to favour a “recent” origin of modern human behaviour (Klein, Reference Klein2019; Mellars, Reference Mellars2010). The criteria for defining and identifying “modernity” vary (see Table 1) but the underlying logic of these hypotheses is often similar. Berwick et al. (Reference Berwick, Friederici, Chomsky and Bolhuis2013, p. 1) set this out clearly in the context of language evolution: “Symbolic behavior, as in cave painting, is an indirect proxy for language, and its earliest indications come from… sites dated at roughly 100 kyr or less… Archaeology thus supports a recent timeframe for the emergence of modern behaviors associated with language: substantially after the emergence of Homo sapiens.” Chronologies differ between sources. Some prefer an earlier date (discussed in McBrearty, Reference McBrearty2013). Others prefer an even later date, and, for instance, Klein (Reference Klein2017) argues that “irrefutable art and personal ornaments, appeared only 50–40 ka, which suggests this was also when full-fledged language appeared” (p. 217). The specific faculties under consideration also vary (see Table 1). Some concentrate on language origins (Tattersall, Reference Tattersall2017a), abstract representation or “complex symbolic thinking” (Klein, Reference Klein2017; Mellars, Reference Mellars2010), and recursive or hierarchical syntax (Bolhuis et al., Reference Bolhuis, Tattersall, Chomsky and Berwick2014; Vyshedskiy, Reference Vyshedskiy2019). Others consider capacities such as systematising thought (Baron-Cohen, Reference Baron-Cohen2020), working memory (Wynn et al., Reference Wynn, Coolidge and Bright2009; Wynn & Coolidge, Reference Wynn and Coolidge2010), imagination, creativity, and neural connectivity (Wadley, Reference Wadley2021) or cognitive fluidity (Mithen, Reference Mithen, Hatfield and Pittman2013).

Table 1.

Noncomprehensive table of proposed criteria evidencing different aspects of modern behaviour and cognition. The current investigation focusses on symbolic evidence, broadly construed, although the same dataset could be coded to address other evidence types

There are different views on whether cognitive change occurs via genetic/somatic/neural differences or via culturally transmissible extrasomatic inventions. Some contend that any “revolution” in human cognitive ability was accompanied by change in the substrates of the brain (Klein, Reference Klein2008, Reference Klein2017, Reference Klein2019; Wynn et al., Reference Wynn, Coolidge and Bright2009 and, with caveats, Mellars, Reference Mellars2005). Others suggest that the “capacity for culture” (Kelly et al., Reference Kelly, Mackie and Kandel2023) or the “language-ready brain” (Bolhuis et al., Reference Bolhuis, Tattersall, Chomsky and Berwick2014; Tattersall, Reference Tattersall2017a) evolved alongside archaic H. sapiens, and enabled but pre-dated language or certain forms of cultural expression. Many such theories still predict somatic, neural, or other intrinsic capacity differences between H. sapiens and Neanderthals (Tattersall, Reference Tattersall2017a), or between earlier and later H. sapiens (Kelly et al., Reference Kelly, Mackie and Kandel2023). Some see cultural and somatic evolution as being intertwined and propose a gene–culture feedback loop between capacity and expression (Wadley, Reference Wadley2021). Some separate “behavioural modernity” from somatic change or intrinsic capacities entirely: Sterelny (Reference Sterelny2011), for instance, sees behavioural modernity not as “coded and canalised” but as an extrinsic “collective capacity to retain and upgrade rich systems of information and technique” (p. 814), which is “dependent on the organization of social life” (p. 819).

Beyond the academy, “recent origins” theories have been influential in shaping public perceptions of prehistory. Certain popular texts such as Sapiens: A Brief History of Humankind (Harari, Reference Harari2014), its graphic adaptation (Harari, Vandermuelen, & Casanave, Reference Harari, Vandermuelen and Casanave2020), and others (e.g., Baron-Cohen, Reference Baron-Cohen2020), present the “recent origins” model of language as a resolved consensus theory. For example, Harari et al. (Reference Harari, Vandermuelen and Casanave2020, p. 61) state that after 70,000 ka we see “the first objects that we can reliably call jewellery” which “most researchers say… came down to a revolution in sapiens’ cognitive abilities.” Although not all popular texts promote this view (Graeber & Wengrow, Reference Graeber and Wengrow2021; Sykes, Reference Sykes2020), those that do have been highly influential, and nativist (sensu Sterelny, Reference Sterelny2019) recent origins theories have filtered into other forms of popular media (Kurzgesagt, 2016).

Within the academy, recent origins and “revolution” theories have been vigorously debated. Some propose a deep origin of sophisticated linguistic ability (e.g., Albessard-Ball & Balzeau, Reference Albessard-Ball and Balzeau2018; Mounier et al., Reference Mounier, Noûs and Balzeau2020). Many highlight earlier artefactual evidence of symbolic behaviour (McBrearty, Reference McBrearty2013; McBrearty & Brooks, Reference McBrearty and Brooks2000), especially outside of Europe (McBrearty & Stringer, Reference McBrearty and Stringer2007). Evidence of symbolism associated with Neanderthals (e.g., Hoffmann et al., Reference Hoffmann, Standish, García-Diez, Pettitt, Milton and Zilhao2020; Nowell, Reference Nowell, G. and Pittman2013; Zilhão et al., Reference Zilhão, Angelucci, Badal-García, D'Errico, Daniel, Dayet and Zapata2010) – who diverged from H. sapiens 700–400 ka (see Stringer, Reference Stringer2016) – has fuelled phylogenetic arguments for early origins of symbolic capacity (see Leder et al., Reference Leder, Hermann, Hüls, Russo, Hoelzmann, Nielbock and Terberger2021; Mellars, Reference Mellars2010; Zilhão, Reference Zilhão2007).

Some have questioned the extent to which specific artefacts actually do evidence linguistic ability or symbolic capacity (Botha, Reference Botha2010; Kuhn & Stiner, Reference Kuhn and Stiner2007; Sterelny, Reference Sterelny2011, Reference Sterelny2014). Ochre, for instance may have prosaic and functional uses, for example as camouflage, insect repellent, an adhesive (Sterelny, Reference Sterelny2011; Wadley, Reference Wadley2005), or a threat display (Kuhn & Stiner, Reference Kuhn and Stiner2007; Sterelny, Reference Sterelny2011). Similarly, the link between material culture and certain aspects of syntactic or linguistic ability is not concrete (Botha, Reference Botha2010; Henshilwood & Dubreuil, Reference Henshilwood and Dubreuil2011; Sterelny, Reference Sterelny2014). Personal adornment may engage different neural systems to those employed in creating and decoding spoken utterances (Sterelny, Reference Sterelny2014) and, for instance, children's understanding of symbols does not parallel the ontogeny of syntax (Henshilwood & Dubreuil, Reference Henshilwood and Dubreuil2011).

Others have highlighted more general difficulties in reading the material record (Ames et al., Reference Ames, Riel-Salvatore and Collins2013; Dibble et al., Reference Dibble, Holdaway, Lin, Braun, Douglass, Iovita and Sandgathe2017; Haidle, Reference Haidle, Haidle, Conard and Bolus2016; Scerri & Will, Reference Scerri and Will2023; Shea, Reference Shea2011b; Speth, Reference Speth2004; Zilhão et al., Reference Zilhão, Angelucci, Badal-García, D'Errico, Daniel, Dayet and Zapata2010), including the risks of ignoring differences in preservation environments and material choices (Langley, Clarkson, & Ulm, Reference Langley, Clarkson and Ulm2011; Shea, Reference Shea2011b), the risk of overattributing manufacturer intent to the structure of assemblages (Dibble et al., Reference Dibble, Holdaway, Lin, Braun, Douglass, Iovita and Sandgathe2017), the risk of creating false dichotomies and thresholds (Ames et al., Reference Ames, Riel-Salvatore and Collins2013), the inferential gap between performance and capacity (Haidle, Reference Haidle, Haidle, Conard and Bolus2016), and the related risk of using absent evidence to infer absent capacity (Speth, Reference Speth2004; Zilhão, Reference Zilhão2007).

Both primate and hunter–gatherer archaeologists have considered the importance of perishable media (Milks, Reference Milks2020; Pascual-Garrido & Almeida-Warren, Reference Pascual-Garrido and Almeida-Warren2021) and contended that complex perishable technologies substantially pre-date even the earliest lithic industries (Pascual-Garrido & Almeida-Warren, Reference Pascual-Garrido and Almeida-Warren2021). There has been extensive debate about the extent to which behavioural modernity and language are intrinsic (e.g., Klein, Reference Klein2019; Mellars, Reference Mellars2010) or culturally acquired (Sterelny, Reference Sterelny2011, Reference Sterelny2016; Tattersall, Reference Tattersall2017b). Cultural transmission of technologies (Speth, Reference Speth2004) and the role of population size and structure in driving innovation are presented as alternative hypotheses to somatic change (Henrich, Reference Henrich2004; Henrich et al., Reference Henrich, Boyd, Derex, Kline, Mesoudi, Muthukrishna and Thomas2016; Powell, Shennan, & Thomas, Reference Powell, Shennan and Thomas2009; Scerri & Will, Reference Scerri and Will2023; Sterelny, Reference Sterelny2021a; but see Klein & Steele, Reference Klein and Steele2013; Vaesen, Collard, Cosgrove, & Roebroeks, Reference Vaesen, Collard, Cosgrove and Roebroeks2016). Others argue that differences in material culture should be conceptualised not as markers of changing cognition, but as responses to varying environments (d'Errico & Stringer, Reference d'Errico and Stringer2011; Hopkinson, Reference Hopkinson, Roberts and Vander Linden2011; Shea, Reference Shea2011b) – although material variability has, itself, sometimes been used to chart cognitive evolution (see, e.g., discussion by Nowell & White, Reference Nowell, White, Nowell and Davidson2010; Shea, Reference Shea2017; Tennie, Braun, Premo, & McPherron, Reference Tennie, Braun, Premo, McPherron, Haidle, Conard and Bolus2016; Wadley, Reference Wadley, Haidle, Conard and Bolus2016). Several have pointed to the difficulties of defining cognitive and linguistic “modernity” (d'Errico, Reference d'Errico2003; Shea, Reference Shea2011b; Stringer, Reference Stringer2002) or otherwise critiqued the notion of behavioural modernity as an analytically useful concept (Ames et al., Reference Ames, Riel-Salvatore and Collins2013; Scerri & Will, Reference Scerri and Will2023; Shea, Reference Shea2011b).

Despite continued discourse concerning recent origins theories (d'Errico et al., Reference d'Errico, Pitarch Martí, Shipton, Le Vraux, Ndiema, Goldstein and Boivin2020; Klein, Reference Klein2017; Scerri & Will, Reference Scerri and Will2023), over the last decade, research consensus has leaned towards gradualistic (McBrearty, Reference McBrearty2013) and mosaic (Conard, Reference Conard, Henke and Tattersall2015; Scerri et al., Reference Scerri, Thomas, Manica, Gunz, Stock, Stringer and Chikhi2018) theories of evolutionary change. Pure cultural evolutionary accounts, which assume no difference in intrinsic capacity, either within our species (Tattersall, Reference Tattersall2017a), or more broadly (Sterelny, Reference Sterelny2016, Reference Sterelny2019) have become more widely accepted. Focus has also shifted to explorations of species-level differences (Wynn, Overmann, & Coolidge, Reference Wynn, Overmann and Coolidge2016). Here too, however, discussions of symbolism and complexity in material culture are still at the fore. Both cord making and birch pitch tar production have been pivotal to debates about Neanderthal cognition and planning depth (see Hardy et al., Reference Hardy, Moncel, Kerfant, Lebon, Bellot-Gurlet and Mélard2020; Kozowyk et al., Reference Kozowyk, Soressi, Pomstra and Langejans2017; Schmidt et al., Reference Schmidt, Blessing, Rageot, Iovita, Pfleging, Nickel and Tennie2019). Neanderthal personal adornment (Finlayson et al., Reference Finlayson, Brown, Blasco, Rosell, Negro, Bortolotti and Rodríguez Llanes2012), burial (Pomeroy et al., Reference Pomeroy, Bennett, Hunt, Reynolds, Farr, Frouin and Barker2020), art (Hoffmann et al., Reference Hoffmann, Standish, García-Diez, Pettitt, Milton, Zilhão and Pike2018; White et al., Reference White, Bosinski, Bourrillon, Clottes, Conkey, Rodriguez and Willis2020), nonsubsistence-related faunal assemblages (Baquedano et al., Reference Baquedano, Arsuaga, Pérez-González, Laplana, Márquez, Huguet and Higham2023), and musical instruments (Turk et al., Reference Turk, Turk, Dimkaroski, Blackwell, Horusitzky, Otte and Korat2018) are frequently used as evidence both for (Breyl, Reference Breyl2021; Hardy et al., Reference Hardy, Moncel, Kerfant, Lebon, Bellot-Gurlet and Mélard2020) and against (Schmidt et al., Reference Schmidt, Blessing, Rageot, Iovita, Pfleging, Nickel and Tennie2019; Wynn et al., Reference Wynn, Overmann and Coolidge2016) Neanderthals possessing, for example, “symbolic thought” or “modern human” cognitive capacity. These recent debates have fruitfully challenged assumptions (Baquedano et al., Reference Baquedano, Arsuaga, Pérez-González, Laplana, Márquez, Huguet and Higham2023; Breyl, Reference Breyl2021) that Neanderthals had less advanced (see, e.g., Mithen, Reference Mithen, Akazawa, Ogihara, Tanabe and Terashima2014; Speth, Reference Speth2004) or substantively different (see, e.g., Wynn et al., Reference Wynn, Overmann and Coolidge2016) cognitive capacities to modern H. sapiens; but they yet risk perpetuating the assumption that material evidence of complexity is necessary for past populations to be considered cognitively modern.

4. Absence of evidence, evidence of absence, denying the antecedent and the primitive null

Given the limited evidence available, it is important to squeeze “every last bit of data… from the archaeological record” (Overmann & Coolidge, Reference Overmann and Coolidge2019, p. 6). However, when considered in light of contemporary forager ethnography, it becomes clear that there are inferential difficulties in linking cognition to material culture. Contemporary foragers are just as cognitively sophisticated as other contemporary human populations. Yet, even despite access to metals and plastics, alongside extensive exchange with neighbouring agricultural groups in goods and ideas, many have artefact sets smaller and less elaborate than those associated with Upper Palaeolithic Europe. Many do not routinely create paintings, bury their dead with symbolic grave goods (Woodburn, Reference Woodburn, Bloch and Perry1982), create ochre-based pigments, or engage in certain other activities used as proxies (Henshilwood & Dubreuil, Reference Henshilwood, Dubreuil, Knight and Botha2009; Klein, Reference Klein2017; Mellars, Reference Mellars2005; Wadley, Reference Wadley2021) for past behavioural complexity.

Thus, the use of material cultural in charting the trajectory of cognitive evolution appears to represent a “denying the antecedent” fallacy: That is, where “A” implies “B,” it does not follow that “not A” implies “not B.” In other words, although evidence of sophisticated material culture might provide positive evidence of cognitive sophistication (Finlayson et al., Reference Finlayson, Brown, Blasco, Rosell, Negro, Bortolotti and Rodríguez Llanes2012; Haidle, Reference Haidle, Haidle, Conard and Bolus2016; Lombard & Haidle, Reference Lombard and Haidle2012; but see Botha, Reference Botha2010; Sterelny, Reference Sterelny2014), the inverse – that a lack of sophisticated material culture demonstrates a lack of cognitive sophistication – is unproven. It is unclear whether complex “modern” human cognition requires evidence of burial, art, symbolism, or complex technology. Such evidence may be sufficient to prove (though, see, e.g., Botha, Reference Botha2008, Reference Botha2010; Sterelny, Reference Sterelny2014), but is not a necessary condition of cognitive complexity (see Ames et al., Reference Ames, Riel-Salvatore and Collins2013; Haidle, Reference Haidle, Haidle, Conard and Bolus2016; Hopkinson, Reference Hopkinson, Roberts and Vander Linden2011; Scerri & Will, Reference Scerri and Will2023; Shea, Reference Shea2011b; Speth, Reference Speth2004, among others). This distinction is captured by the well-known aphorism “absence of evidence is not evidence of absence.”

Indeed, most scholars of cognitive prehistory are careful to acknowledge the limitations of the archaeological record (Kelly et al., Reference Kelly, Mackie and Kandel2023; Mellars, Reference Mellars2010; Shultz, Nelson, & Dunbar, Reference Shultz, Nelson and Dunbar2012; Wadley, Reference Wadley2013). Bolhuis et al. (Reference Bolhuis, Tattersall, Chomsky and Berwick2014) highlight that “inference from the symbolic record… rests on evidence that is necessarily quite indirect” (p. 4), whereas Mellars (Reference Mellars2010) cautions against “pressing the evolutionary and cognitive implications of all this too far” (p. 20148). Kelly highlights that “the empirical record is difficult to read as a straightforward document” (p. 6). Sterelny (Reference Sterelny2016) makes clear that inferences from technology, demographic conditions, trade networks, and movement patterns can only paint a “fragmentary and fallible” picture “of long-vanished hominins” (p. 183). Wadley (Reference Wadley, Haidle, Conard and Bolus2016) cautions that “we can only interpret levels of cultural or cognitive complexity from circumstantial evidence.” Almost all are aware of the interpretive difficulties inherent in reconstructing past minds from material traces. Yet, although alive to these difficulties, many continue to overinterpret the material record. Here, I describe three recurring issues: (1) The unproven assumption that modern humans will inevitably create certain categories of enduring material evidence, diagnostic of their modernity; (2) the use of absent evidence and absence–presence transitions to advance positive hypotheses about transitions in human minds or brains; and (3) the (null) assumption that, without positive evidence to the contrary, early H. sapiens or other human species are primitive by default.

First, several researchers explicitly contend that cognitively modern humans would inevitably have created sophisticated artefacts from enduring media (Klein, Reference Klein2017; Mithen, Reference Mithen, Hatfield and Pittman2013). Mithen expresses this directly, stating “it appears intuitively unlikely that such artistic and symbolic activities might have been expressed in such inorganic and non-enduring material without having been expressed in bone and stone” (p. 223). Aronoff (Reference Aronoff, Aronoff and Rees-Miller2020) makes a similar claim regarding language evolution, arguing “a relatively sudden jump in the complexity of human linguistic behavior, if it occurred, should leave immediate traces in the archeological record in the shape of a sudden jump in the complexity of preserved artefacts (tools, ornaments, and artwork)” (p. 6). Similarly, Kelly et al. (Reference Kelly, Mackie and Kandel2023), although they make clear that there “were many prehistoric societies whose members were fully capable of symbolic expression but who (apparently) left behind few obviously symbolic artifacts” (p. 5), also provide a qualified restatement of the same argument: “We provisionally assume that a population cognitively capable of symbolic expression through activities that leave no trace will also participate in those that do” (p. 2). They speculate, on this basis, that a cognitive capacity for culture appeared between 195 and 130 ka.

Second, and more commonly, researchers draw directly on absent material evidence or shifts from an absence to a presence of certain artefacts to make strong inferences about the chronology and trajectory of cognitive evolution. Klein (Reference Klein2017) argues for rapid cognitive advancements only in the Later Stone Age because “proposed symbolic artefacts do not occur in most MSA [Middle Stone Age] sites” (p. 216). Wadley (Reference Wadley2021) highlights the paucity of signs of imaginative technological development before 100 ka (“We see few skills in the pre-100 ka ago record that could not easily be passed on through nonverbal observation,” p. 131). She suggests that this paucity, relative to “the proliferation innovative material culture after 100 ka” evidences the late appearance of “complex cognition and brains with neural connectivity like ours” (p. 134). Coolidge et al. (Reference Coolidge, Wynn, Overmann, Alloway and Alloway2012) consider and then explicitly dismiss concerns over arguing from absent evidence, concluding these set “too strict” a standard which “places unreasonable demands on archaeological inference” (p. 16). They instead interpret the shift in the Upper Palaeolithic material record around 50,000, and the associated appearance of ivory carvings, as implying a “cognitive ‘leap’… consistent with an enhancement to WM [working memory] through a genetic or epigenetic event” (p. 17).

Similar absence-to-presence logic is often employed in consideration of earlier lithic evidence also and, for instance, several studies (Stout & Chaminade, Reference Stout and Chaminade2012; Stout, Chaminade, Apel, Shafti, & Faisal, Reference Stout, Chaminade, Apel, Shafti and Faisal2021) have leveraged brain imaging data to quantify technical complexity in the manufacture of Acheulean and Oldowan lithics and to infer changes in capacity. Stout and Chaminade (Reference Stout and Chaminade2012) suggest that because “Lower Palaeolithic technology is relatively lacking in semantic content… this aspect of modern human cognition evolved later” (p. 83). Nor is such logic limited to genetic or intrinsic capacity models. Sterelny (Reference Sterelny2016) uses lacking “technical achievements” and the absence of “overt signs of an ideological life” including ochre, jewellery, “figurines or other objects made for non-utilitarian purpose” (p. 179) as one of the four categories of evidence to infer that Homo heidelbergensis probably did not possess “lexically rich protolanguage” (p. 179). He contends that “if they were standard features of mid-Pleistocene hominin life, it is likely that we would see those traces” (p. 179).

Most researchers do not dismiss the inferential problems of arguing from absent evidence (Coolidge et al., Reference Coolidge, Wynn, Overmann, Alloway and Alloway2012), or employ absent evidence to advance their theses. Almost all recognise that we cannot determine whether changes in material culture are “the result of a cognitive advance or a more mundane process” (Shultz et al., Reference Shultz, Nelson and Dunbar2012, p. 2137). More commonly, however, assumptions about the cognitive capacities of ancient humans are implicit. For to invoke artefactual evidence (Barham & Everett, Reference Barham and Everett2021; Conard, Reference Conard, Henke and Tattersall2015; Coolidge, Haidle, Lombard, & Wynn, Reference Coolidge, Haidle, Lombard and Wynn2016; Henshilwood & Dubreuil, Reference Henshilwood and Dubreuil2011; Kelly et al., Reference Kelly, Mackie and Kandel2023; Muller, Clarkson, & Shipton, Reference Muller, Clarkson and Shipton2017; Stout et al., Reference Stout, Chaminade, Apel, Shafti and Faisal2021; Wadley et al., Reference Wadley, Esteban, De La Peña, Wojcieszak, Stratford, Lennox and Sievers2020) in establishing a chronology for cognitive evolution, or in comparing human species (Leder et al., Reference Leder, Hermann, Hüls, Russo, Hoelzmann, Nielbock and Terberger2021; Schmidt et al., Reference Schmidt, Blessing, Rageot, Iovita, Pfleging, Nickel and Tennie2019; Sykes, Reference Sykes, Coward, Hosfield, Pope and Wenban-Smith2015), is to tacitly endorse the assumption that without such positive evidence to the contrary, past humans should not be considered cognitively or behaviourally sophisticated by default.

This third tacit assumption, the “primitive,” “plesiomorphic,” or “ancestral” null, is pervasive. It is seen in depictions of the Neanderthals, who had cutting tools and cord-making technologies (Hardy et al., Reference Hardy, Moncel, Kerfant, Lebon, Bellot-Gurlet and Mélard2020) yet are habitually shown in museum reconstructions with untended hair or few-to-no clothes. It is seen in discussions surrounding Neanderthal extinction, which often attend to cognitive difference (Gilligan, Reference Gilligan2007; Gilpin, Feldman, & Aoki, Reference Gilpin, Feldman and Aoki2016; Horan, Bulte, & Shogren, Reference Horan, Bulte and Shogren2005; Villa & Roebroeks, Reference Villa and Roebroeks2014). It is seen in the disproportionate attention and impact generated by finds that push “complex” or representational expressions further into the past (Aubert et al., Reference Aubert, Lebe, Oktaviana, Tang, Burhan, Hamrullah and Brumm2019; Barham et al., Reference Barham, Duller, Candy, Scott, Cartwright, Peterson and Nkombwe2023; Brumm et al., Reference Brumm, Oktaviana, Burhan, Hakim, Lebe, Zhao and Aubert2021; Hoffmann et al., Reference Hoffmann, Standish, García-Diez, Pettitt, Milton, Zilhão and Pike2018; Schmidt et al., Reference Schmidt, Blessing, Rageot, Iovita, Pfleging, Nickel and Tennie2019) and in the popular and scholarly discourses surrounding them (Hoffmann et al., Reference Hoffmann, Standish, García-Diez, Pettitt, Milton and Zilhao2020; Metcalfe, Reference Metcalfe2023; Mithen, Reference Mithen, Akazawa, Ogihara, Tanabe and Terashima2014; Sample, Reference Sample2018; Schmidt et al., Reference Schmidt, Blessing, Rageot, Iovita, Pfleging, Nickel and Tennie2019; White et al., Reference White, Bosinski, Bourrillon, Clottes, Conkey, Rodriguez and Willis2020; Wynn et al., Reference Wynn, Overmann and Coolidge2016, Reference Wynn, Overmann and Malafouris2021). Indeed, in an interview for the Scientific American (Metcalfe, Reference Metcalfe2023) concerning the recent discovery of wooden structures from 476 ka in Zambia (Barham et al., Reference Barham, Duller, Candy, Scott, Cartwright, Peterson and Nkombwe2023), the lead author sets out the primitive null clearly, stating “I never would have thought that pre-Homo sapiens would have had the capacity to plan something like this.”

A priori, this ancestral null is not unreasonable. Humans, contrasted with our closest extant relatives, are in numerous regards, highly and perhaps uniquely derived (Foley, Reference Foley2016; Maynard Smith & Szathmáry, Reference Maynard Smith and Szathmáry1997). Moreover, it appears probable that the human–chimpanzee last common ancestor, though plausibly importantly different from any individual living ape (Lovejoy, Reference Lovejoy2009; Püschel, Bertrand, O'Reilly, Bobe, & Püschel, Reference Püschel, Bertrand, O'Reilly, Bobe and Püschel2021; Sayers, Raghanti, & Lovejoy, Reference Sayers, Raghanti and Lovejoy2012 but see Whiten et al., Reference Whiten, McGrew, Aiello, Boesch, Boyd, Byrne and Wrangham2010), had more in common with other extant apes than with H. sapiens (Kinzey, Reference Kinzey1987; McGrew, Reference McGrew2010; Püschel et al., Reference Püschel, Bertrand, O'Reilly, Bobe and Püschel2021; Stanford & Allen, Reference Stanford and Allen1991). However, even assuming a plesiomorphic (i.e., ancestral) common ancestor between 5 (Kumar, Filipski, Swarna, Walker, & Hedges, Reference Kumar, Filipski, Swarna, Walker and Hedges2005) and 12 (Püschel et al., Reference Püschel, Bertrand, O'Reilly, Bobe and Püschel2021) Ma, the trajectory and pace of human cognitive evolution remains unresolved. Although physical evidence is also frequently considered (Shultz et al., Reference Shultz, Nelson and Dunbar2012), current cognitive and linguistic archaeology is yet considerably enmeshed with interpretation of the material record. As such assumptions have historically often proven wrong (Barham et al., Reference Barham, Duller, Candy, Scott, Cartwright, Peterson and Nkombwe2023; Breyl, Reference Breyl2021; Harmand et al., Reference Harmand, Lewis, Feibel, Lepre, Prat, Lenoble and Roche2015; Hoffmann et al., Reference Hoffmann, Standish, García-Diez, Pettitt, Milton, Zilhão and Pike2018; McBrearty & Brooks, Reference McBrearty and Brooks2000; Scerri & Will, Reference Scerri and Will2023; Shea, Reference Shea2011b), perhaps our null model should itself be reconsidered.

5. Material culture, symbolism, and cognition from the perspective of contemporary hunter–gatherer research

These inferential problems are conspicuous to hunter–gatherer anthropologists for two reasons. First, as mentioned above, many contemporary foragers do not, for instance, habitually create structures as architecturally sophisticated as the V-shape joinery found at Kalambo Falls (Barham et al., Reference Barham, Duller, Candy, Scott, Cartwright, Peterson and Nkombwe2023), nor as intricate as the ivory figurines of the Upper Palaeolithic (Conard, Reference Conard2009; Coolidge et al., Reference Coolidge, Wynn, Overmann, Alloway and Alloway2012; Hahn, Reference Hahn1986; though see Fig. 1). The difficulties of interpreting of such materials are thus more immediately apparent. Second, foragers have faced discrimination (Woodburn, Reference Woodburn1997), often on grounds that their technologies and subsistence practices are atavistic, anachronistic, or primitive (consider, e.g., Bagshawe, Reference Bagshawe1925, pp. 120–121), a narrative that has had weighty material consequences (Elkins, Reference Elkins2022; Layton, Reference Layton, Panter-Brick, Rowley-Conwy and Layton2001; Ndagala, Reference Ndagala1985). Although preconceptions about living foragers have shifted, in considerations of past humans, similar tacit assumptions go unchecked, often unnoticed, making it especially important to explicitly interrogate the utility, perhaps sterility, of the material record in cognitive benchmarking.

Figure 1.

Top: Illustration of Mbuti bark cloth (pongo), reprinted from Tanno (Reference Tanno1981). Bottom: Photograph of a Hadza unfired clay doll (olanakwiko), reprinted from Skaanes (Reference Skaanes2015). Both could be interpreted as signifying a sophisticated capacity for abstract thought, but neither would leave any long-lasting material evidence under normal conditions of preservation.

This logical wrinkle – that modern humans need not leave any palpable material trace of their modernity – is interpretively important but difficult to demonstrate empirically. This is especially true in archaeological datasets that, by dint of uneven preservation, are normally incomplete. To better illustrate this issue, it is necessary to incorporate other forms of evidence, including ethnographic evidence, and to calibrate our expectations about past material complexity with data from modern populations for whom toolsets are comprehensively documented.

Although certain researchers have made this precise point (e.g., Haidle, Reference Haidle, Haidle, Conard and Bolus2016; Sterelny, Reference Sterelny2021b), such discussions have often focussed on the Australian continent (Balme, Davidson, McDonald, Stern, & Veth, Reference Balme, Davidson, McDonald, Stern and Veth2009; Hiscock, Reference Hiscock2007), and particularly the indigenous people of Tasmania (Haidle, Reference Haidle, Haidle, Conard and Bolus2016; Oswalt, Reference Oswalt1976) whose material culture is sometimes framed as an aberrant case of cultural loss (Henrich, Reference Henrich2004). Moreover, discussions have been, by-and-large, nonquantitative (Haidle, Reference Haidle, Haidle, Conard and Bolus2016) and often appear as asides or footnotes (Hiscock, Reference Hiscock2007; Kelly et al., Reference Kelly, Mackie and Kandel2023; Sterelny, Reference Sterelny2021b). There is a clear need to illustrate the problem using a quantitative, data-driven approach.

This article explores three near-comprehensive material culture datasets from modern African foragers, representing a substantial proportion of contemporary African hunter–gatherer diversity. It investigates (1) how much evidence (assuming normal conditions of preservation) these modern human populations would leave of their artefactual repertoires, and (2) whether there are processes, unrelated to cognition, that affect the likelihood of symbolic and other artefacts leaving an enduring signature.

Although researchers have employed numerous lines of evidence to trace the emergence of complex cognition in the archaeological record (Table 1), including material transport (Wilkins et al., Reference Wilkins, Schoville, Pickering, Gliganic, Collins, Brown and Hatton2021), composite tool production (Barham, Reference Barham2013; Coolidge et al., Reference Coolidge, Haidle, Lombard and Wynn2016), and other types of technological complexity (Murray et al., Reference Murray, Harris, Oestmo, Martin and Marean2020; Sykes, Reference Sykes, Coward, Hosfield, Pope and Wenban-Smith2015; Wadley et al., Reference Wadley, Esteban, De La Peña, Wojcieszak, Stratford, Lennox and Sievers2020), evidence of prehistoric symbolism is frequently the most prominent (Leder et al., Reference Leder, Hermann, Hüls, Russo, Hoelzmann, Nielbock and Terberger2021; Sehasseh et al., Reference Sehasseh, Fernandez, Kuhn, Stiner, Mentzer, Colarossi and Longet2021; Wilkins et al., Reference Wilkins, Schoville, Pickering, Gliganic, Collins, Brown and Hatton2021), and is often at the forefront of both academic discourse (Baquedano et al., Reference Baquedano, Arsuaga, Pérez-González, Laplana, Márquez, Huguet and Higham2023; Hoffmann et al., Reference Hoffmann, Standish, García-Diez, Pettitt, Milton, Zilhão and Pike2018; Kelly et al., Reference Kelly, Mackie and Kandel2023; Klein, Reference Klein2017; McBrearty, Reference McBrearty2013; Mithen, Reference Mithen, Akazawa, Ogihara, Tanabe and Terashima2014; Pomeroy et al., Reference Pomeroy, Bennett, Hunt, Reynolds, Farr, Frouin and Barker2020; Tattersall, Reference Tattersall2017a; Wadley, Reference Wadley2021; White et al., Reference White, Bosinski, Bourrillon, Clottes, Conkey, Rodriguez and Willis2020) and popular accounts (Harari, Reference Harari2014; Harari et al., Reference Harari, Vandermuelen and Casanave2020). For ease of coding, analysis, and discussion, therefore, the present investigation focusses primarily on “symbolic evidence,” broadly defined (sect. 8). Despite this focus, current conclusions are generalisable to other categories of evidence also.

Researchers also differ in whether they attribute purported cognitive differences primarily to soma, culture, or both. Some directly invoke genetic/neural differences, “novel gene constellations” (Klein, Reference Klein2019, p. 179) or differences in capacity or potential (Klein, Reference Klein2017, Reference Klein2019; Mellars, Reference Mellars2010; Mithen, Reference Mithen, Hatfield and Pittman2013; Wynn et al., Reference Wynn, Overmann and Coolidge2016), some invoke mixed models involving both cultural and somatic change (Conard, Reference Conard2010; Kelly et al., Reference Kelly, Mackie and Kandel2023; Knight, Reference Knight, Frey, Störmer and Willführ2010; Wadley, Reference Wadley2013, Reference Wadley2021), and some prefer purely cultural evolutionary models that make no strong claims about genes, innate capacities, or brains (Sterelny, Reference Sterelny2017; Sutton, Reference Sutton and Hodder2020). More attention is paid, throughout, to the interpretive problems inherent in the first two categories of model, although consideration is given, in section 14, to pure cultural evolution models also.

The findings presented here demonstrate, empirically, that complex cognition does not necessitate extensive symbolic material culture, and that certain schemata for identifying behavioural modernity (intrinsic or otherwise) would risk excluding contemporary humans. Moreover, results highlight the primacy of extragenetic factors, including ecology, demography, artefact function, and residential mobility, and the limitations each place on artefact repertoire size and material selection (see Collard et al., Reference Collard, Buchanan, Morin and Costopoulos2011; Collard, Kemery, & Banks, Reference Collard, Kemery and Banks2005; Henrich, Reference Henrich2004; Shott, Reference Shott1986; Sterelny, Reference Sterelny2021a; Torrence, Reference Torrence and Bailey1983). Drawing on these data, I emphasise the difficulties of using past material culture, especially symbolic material culture, as an evolutionary yardstick, and the associated risk of falsely inferring that past humans who did not leave certain types of enduring evidence also lacked certain cognitive capacities.

6. Three forager datasets: The Hadza, the Mbuti, and the G//ana

Although many populations around the world subsist by hunting and gathering (Lee & Daly, Reference Lee and Daly1999), holistic material culture datasets have been collated for a smaller number. The data used here were drawn from ethnographic accounts of material culture among three sub-Saharan African foragers, the Botswanan G//ana (Tanaka, Reference Tanaka1979), the Congolese Mbuti (Tanno, Reference Tanno1981), and the Tanzanian Hadza (Marlowe, Reference Marlowe2010; Skaanes, Reference Skaanes2015; Smith, Reference Smith1977; Woodburn, Reference Woodburn1970). The author's field research is with the Hadza (Stibbard-Hawkes, Attenborough, & Marlowe, Reference Stibbard-Hawkes, Attenborough and Marlowe2018, Reference Stibbard-Hawkes, Attenborough, Mabulla and Marlowe2020, Reference Stibbard-Hawkes, Smith and Apicella2022), and I augmented Hadza data with first-hand observation. As with any contemporary human population, all three groups in this study have complex systems of cosmological belief (Ichikawa, Reference Ichikawa1998; Skaanes, Reference Skaanes2015; Solomon, Reference Solomon1997; Stagnaro, Stibbard-Hawkes, & Apicella, Reference Stagnaro, Stibbard-Hawkes and Apicella2022), myths, oral histories (Kohl-Larsen, Reference Kohl-Larsen1956; Osaki, Reference Osaki2001), rituals (Bundo, Reference Bundo2001; Skaanes, Reference Skaanes2015; Turnbull, Reference Turnbull2015), and musical traditions (Bundo, Reference Bundo2001; Marlowe, Reference Marlowe2010; Nurse, Reference Nurse1972). All have fully recursive languages that are phonologically and syntactically complex (e.g., Sands & Güldemann, Reference Sands, Güldemann, Botha and Knight2009; Vossen, Reference Vossen2013).

These populations were chosen for four reasons. First, records of material culture were of a consistent high quality and sources were comprehensive in description of artefact function and material. Two sources (Tanaka, Reference Tanaka1979; Tanno, Reference Tanno1981) were by members of the same research group, and so coded similarly. Second, the three study populations are from different parts of Africa, East (Hadza), South-West (G//ana), and Central (Mbuti) and represent all major regions of the continent where there exist well-described contemporary foragers. Third, the study populations represent at least two important ecotypes: The Hadza and the G//ana both have traditionally lived in savannah bushland environments, and the Mbuti in rainforest environments. Fourth, there exists little uncontested (Sands & Güldemann, Reference Sands, Güldemann, Botha and Knight2009) evidence for a close linguistic or phylogenetic link between the three groups, and each are from different parts of the continent with no recent history of interaction, minimising the impact of ancestral (i.e., Galton's problem) and spatial autocorrelation. As our species' origins are in Africa, and as discussions of the “human revolution” have sometimes concentrated on differences between the archaeological records of sub-Saharan Africa and Europe (see, e.g., McBrearty & Brooks, Reference McBrearty and Brooks2000; McBrearty & Stringer, Reference McBrearty and Stringer2007; Mellars, Reference Mellars2005), data from contemporary foragers living in two important African ecologies are apposite.

This dataset included 256 artefacts, 90 from the Hadza, 97 from the Mbuti, and 69 from the G//ana, comprising 362 discrete components, made from 48 distinct materials. The majority of artefacts (190) had no components obtained from trade, whereas a minority (65) included traded materials. As technologies may be regularly invented and lost, complete repertoires are probably impossible, although these inventories are as close to comprehensive as any that exist.

Today, subsistence patterns are changing. The G//ana have largely abandoned traditional foraging practices (Osaki, Reference Osaki2001). The Hadza are presently undergoing a rapid shift towards mixed subsistence (Pollom, Cross, Herlosky, Ford, & Crittenden, Reference Pollom, Cross, Herlosky, Ford and Crittenden2021; Stibbard-Hawkes & Apicella, Reference Stibbard-Hawkes and Apicella2022). Many Mbuti continue to hunt with nets, although regularly supplement their diets with food obtained from neighbouring farmers, of whom there are an increasing number (Terashima & Ichikawa, Reference Terashima and Ichikawa2003). When study data were collected, however, each subsisted primarily through hunting and gathering.

Most bush-living Hadza before the early 2000s attained more than 90% of their calories through foraging. Accounts of Hadza material culture have been remarkably consistent in sources dating back to the early 1900s (see Marlowe, Reference Marlowe2010), as have reports of Hadza subsistence practices and demography (Blurton Jones, Reference Blurton Jones2016; Marlowe, Reference Marlowe2010). Among the G//ana there were reports, from the mid-to-late 1970s, of permanent G//ana “basecamps” where people practiced mixed foraging alongside minor seasonal horticulture and kept livestock (Cashdan, Reference Cashdan1984). However, between 1966 and 1974, when study data were collected (Tanaka, Reference Tanaka1979), horses had not been widely adopted (Osaki, Reference Osaki2001), people subsisted largely by foraging and moved residences frequently (Tanaka, Reference Tanaka1979). For the Mbuti, by 1974, when present data were collected (Tanno, Reference Tanno1981), though there was little wage labour, itinerant traders visited most camps (Hart, Reference Hart1978) and traded crops, iron, and tobacco for foraged goods. This intensified hunting, although did not otherwise impact hunting and foraging techniques or cause other documented technological change (Hart, Reference Hart1978).

None of these populations have historically been isolated, and all have traded and interacted with neighbouring farmers and pastoralists for as long as there are records (e.g., Marlowe, Reference Marlowe2010; Osaki, Reference Osaki2001; Terashima & Ichikawa, Reference Terashima and Ichikawa2003). In certain tools, traded materials such as iron and plastics have replaced traditional media such as wood and stone. There are also some instances of minor technological exchange between these populations and their neighbours (Nurse, Reference Nurse1972; Tanno, Reference Tanno1981). I highlight and account for these patterns when relevant.

7. Tool component materials and taphonomic signatures

To investigate whether a particular tool would leave any archaeologically visible trace, it was first necessary to separate each tool into its component materials, and then code each material based on its potential to leave any enduring evidence. I name this variable “taphonomic signature” – “taphonomy” being the study of processes that affect the preservation and recovery of organic, or artefactual (Behrensmeyer, Denys, & Brugal, Reference Behrensmeyer, Denys and Brugal2018) remains.

Tool material coding was primarily based on direct ethnographic descriptions. These had, in most cases (Marlowe, Reference Marlowe2010; Smith, Reference Smith1977; Tanaka, Reference Tanaka1979; Tanno, Reference Tanno1981), already been tabulated by the ethnographer. In a minority of cases the presence of a particular material was inferred but not documented. For example, many Hadza leather items are stitched with bark thread, but this was sometimes (e.g., knife sheaths) not mentioned. In such cases, the material was recorded but coded as “inferred.” Such materials were only listed when there was good evidence, and inferred materials were included in the final analysis. One item, a Hadza ritual cloak, though probably made of leather, was excluded from analysis as there was insufficient textual evidence to support this inference.

To account for materials only available through trade, I created a “traded” variable. Materials were coded as “traded” where specified by ethnographic accounts or where there was no ethnographically recorded way for those materials to be otherwise acquired (e.g., rubber, plastic, all metals).

For each material, I also coded taphonomic signature as a factor variable. Most plant-derived materials (e.g., wood, bark, fruit shells, seeds, leaves) and processed plant derivatives (e.g., rope, fibre) were coded as having a “weak” taphonomic signature. So too were most animal byproducts (e.g., fur, fat, wax, cocoons). Metals (iron, brass, copper, steel), plastics, and synthetic rubbers were coded as having a “strong” taphonomic signature, as were stone and bone. Shell and horn were an edge case. Although the outer keratinous sheaths of both tortoise shell and most ungulate horns are prone to decomposition (see, e.g., O'Connor, Solazzo, & Collins, Reference O'Connor, Solazzo and Collins2015), the inner bone is not, and ethnographic sources did not make the distinction. I opted to code both horn and tortoise shell as having a strong signature, preferring to overestimate preservation probability. A minority of materials more fragile than bone but not prone to bacterial decomposition (e.g., eggshells, gastropod shells), were initially coded as having a moderate taphonomic signature. As there were few materials of this type, I collapsed moderate and strong to create a binary variable for analysis.

Codings were based on material only and do not account for depositional environment. Except in rare conditions (e.g., anaerobic marsh, permafrost, desert), postdepositional processes tend to reduce information. Given the correct conditions of preservation, even those artefacts coded here as having a “weak” taphonomic signature may leave long-lasting traces (e.g., Barham et al., Reference Barham, Duller, Candy, Scott, Cartwright, Peterson and Nkombwe2023; d'Errico et al., Reference d'Errico, Backwell, Villa, Degano, Lucejko, Bamford and Beaumont2012; Thieme, Reference Thieme1997; Wadley et al., Reference Wadley, Esteban, De La Peña, Wojcieszak, Stratford, Lennox and Sievers2020). However, such conditions are rare and, though taphonomic processes do not cause information loss at a consistent rate (Surovell, Byrd Finley, Smith, Brantingham, & Kelly, Reference Surovell, Byrd Finley, Smith, Brantingham and Kelly2009), preservation probability decreases at greater time depths (Langley, Clarkson, & Ulm, Reference Langley, Clarkson and Ulm2008, Reference Langley, Clarkson and Ulm2011).

The dataset included >45 distinct materials, too many for meaningful statistical analysis. Therefore, to investigate material selection, I collapsed component materials into three categories: plant-derived (e.g., bark, fruit, stems, wood, seeds), animal-derived (e.g., bone, hide, horn, shells, cocoons), or inorganic (e.g., stone, metal, glass, plastics). Only four materials proved difficult to categorise: fungi, coded as “plant-derived”; cloth, coded as “plant-derived”; ash, coded as inorganic (see Karkanas, Reference Karkanas2021, for discussion of ash taphonomy); and rubber, today often synthetic, so coded as “inorganic.” Annotated R code for category conversions is provided in the “Data availability” section.

8. Symbolism and artefact function

I also created a binary variable with the purpose of capturing whether a specific artefact would, by certain schemata (e.g., Klein, Reference Klein2017; Mithen, Reference Mithen, Akazawa, Ogihara, Tanabe and Terashima2014), constitute evidence for complex cognition. This was not straightforward as even those scholars who seek to employ artefactual data in the study of past cognition recognise that inferring cognitive capacities from artefacts is “notoriously tricky” (d'Errico & Henshilwood, Reference d'Errico, Henshilwood, Henshilwood and d'Errico2011, p. 56) and often “more art than science” (Coolidge, Overmann, & Wynn, Reference Coolidge, Overmann, Wynn, Wynn, Overmann and Coolidge2022, p. 1). Evidential criteria vary between authors (Table 1) and definitions are fluid (Stringer, Reference Stringer2002). Some authors employ broad definitions of “modern cognition,” which include complex exchange networks, technological diversification, and hunting strategies (Ames et al., Reference Ames, Riel-Salvatore and Collins2013; Davidson, Reference Davidson2010). Others restrict definitions to symbolic evidence, broadly construed, including ochre use, and decorative modifications such as polishing (e.g., d'Errico & Henshilwood, Reference d'Errico, Henshilwood, Henshilwood and d'Errico2011). Others employ an even narrower definition. Mithen (Reference Mithen, Akazawa, Ogihara, Tanabe and Terashima2014) discounts ochre use. Klein (Reference Klein2017) limits evidence to “unambiguous symbolic artefacts” including “carefully cut, carved and ground” shell beads, and representational art, discounting much earlier symbolic evidence (e.g., ochre fragments; “perforated shells”).

Here, I chose to focus on evidence for symbolism, broadly construed. This is for two reasons. First, symbolic evidence is often highlighted by science communicators (Harari et al., Reference Harari, Vandermuelen and Casanave2020; Kurzgesagt, 2016) and still garners extensive research attention (Kelly et al., Reference Kelly, Mackie and Kandel2023; Leder et al., Reference Leder, Hermann, Hüls, Russo, Hoelzmann, Nielbock and Terberger2021; Vyshedskiy, Reference Vyshedskiy2019) as “the sine qua non of modern human cognitive capability” (McBrearty, Reference McBrearty2013, p. 13). Second, this simple binary variable clearly illustrates the mismatch between actual toolsets and enduring evidence, and the associated risk of false-negative errors. Although symbolism makes a useful focal point for analysis and discussion, however, present inferences also apply to other diagnostic criteria with bases in material evidence (see Table 1).

I coded each artefact in the sample as “symbolic evidence” when that artefact was either ornamented/decorated, was used for personal adornment or music making, or had some other nonutilitarian function or modification. This included all musical instruments, toys, dyes, and pigments, practical items with nonfunctional decorations (e.g., scored arrows, decorated bows), dolls, beads, jewellery (e.g., necklaces, rings), alongside as items of clothing that served no protective, thermoregulatory, or clear utilitarian function (e.g., headbands, decorative belts). Clothing items with a practical purpose and no recorded additional decorative modification were excluded, as were most undecorated subsistence tools, storage containers, utensils, and so on.

Importantly, this variable quantifies whether an item would constitute evidence of symbolism, recognisable to a naive observer. It does not represent an artefact's actual symbolic function. Subsistence items without decorative modification are frequently replete with symbolic meaning (Barham & Everett, Reference Barham and Everett2021; González-Ruibal, Hernando, & Politis, Reference González-Ruibal, Hernando and Politis2011; Wiessner, Reference Wiessner1983). However, such information is unrecoverable without context. It may be, for example, that the Lomekwian or Oldowan lithics had important symbolic functions, although any such meaning is lost to time.

Conversely, the link between symbolic evidence and cognition has, itself, been both contested and debated (Mithen, Reference Mithen, Akazawa, Ogihara, Tanabe and Terashima2014; Shea, Reference Shea2011b; Stringer, Reference Stringer2002). The inferential utility of ochre has been dismissed by numerous scholars (Mithen, Reference Mithen, Akazawa, Ogihara, Tanabe and Terashima2014; Sterelny, Reference Sterelny2011). And although artefacts have been linked by some to grammatical and linguistic ability (Klein, Reference Klein2017; Stout et al., Reference Stout, Chaminade, Apel, Shafti and Faisal2021; Tattersall, Reference Tattersall2017b), others have highlighted the attendant inferential risks and pitfalls of trying to infer syntax or language skills from material representations (Botha, Reference Botha2008, Reference Botha2010; Henshilwood & Dubreuil, Reference Henshilwood and Dubreuil2011; Sterelny, Reference Sterelny2014). Often, sophisticated artefacts need not necessitate sophisticated cognition at all (Sterelny, Reference Sterelny2014) and may be explicable through simple decision rules (Walsh, Hansell, Borello, & Healy, Reference Walsh, Hansell, Borello and Healy2013) and/or sensory stimulation/exploitation (sensu Verpooten & Nelissen, Reference Verpooten and Nelissen2010).

Moreover, the decision to define all artefacts without a definite utilitarian/social function as symbolic, especially, may yield false positives. Toys, for instance, often have pedagogical value (Lew-Levy, Andersen, Lavi, & Riede, Reference Lew-Levy, Andersen, Lavi and Riede2022; Riede, Lew-Levy, Johannsen, Lavi, & Andersen, Reference Riede, Lew-Levy, Johannsen, Lavi and Andersen2023), and for example miniaturised version of adult tools (Lew-Levy et al., Reference Lew-Levy, Andersen, Lavi and Riede2022), such as the small hunting bows given to Hadza children (Marlowe, Reference Marlowe2010) have an explicitly educational purpose. Conversely, children often create art and representational media (Skaanes, Reference Skaanes2015). In cases of doubt I coded against the direction of the study's thesis, employing a broad operational definition of symbolism. As such, present categorisations probably overestimate the extent of symbolic evidence.

To explore whether certain types of tool were more likely to leave a taphonomic signature than others, I also coded tools by their function. These codings were based on ethnographic description and, for some Hadza artefacts, personal observation or discussion with other researchers (Blurton Jones, personal communication, 2020). Each tool could take up to three functions, although the majority (204/256) had only one. The resulting dataset included >25 unique tool functions, too many for useful analysis. These were collapsed into nine categories: (1) Tools used in the preparation/modification of other materials (e.g., hammers, awls, anvils, needles); (2) storage/transport tools (e.g., containers, bags, slings); (3) ritual artefacts and items of personal adornment; (4) tools for play or leisure (e.g., instruments, toys); (5) tools used in grooming, hygiene, or medicine; (6) items of furniture or shelter; (7) foraging tools (e.g., arrows, digging sticks); (8) cooking, eating, and food-preparation tools; and (9) items of clothing or protection.

9. Statistical analysis strategy and outliers

I statistically explored the influence of several predictors (population; symbolic evidence; artefact function; inclusion of traded materials) on (1) probability of artefacts containing enduring materials and (2) material type. The first set of models took taphonomic signature as the outcome, with trade, population, artefact function, and “symbolism” as predictors. As the taphonomic signature variable was coded as a binary, I used binomial regression models for these analyses. Because “symbolism” and artefact function variables contained overlapping information – for example, all items of personal adornment were also classified as symbolic – I substituted these two variables in separate analyses. The second set of categorical models took material type as the outcome, with trade and population as predictors. As material type was a three-factor categorical variable, I used a multinomial model for this analysis. Analyses were conducted in R and STAN using the Bayesian Regression Models (BRMs) package. I set random/varying effects at the population level, as information pooling typically results in better out-of-sample predictive accuracy. Bayesian methods were chosen as, though computationally expensive, and less widely used than their frequentist counterparts, they allow for more intuitive quantification, interpretation, and visualisation of uncertainty in model outputs.

Do note, however, that this analysis uses population-wide tool repertories, and does not account for frequency of production. Thus, although the model outputs reported in Tables 2 and 3 are sufficient to provide broad inferences about population-level patterns, they cannot replicate the fidelity of, for example, a site-level analysis of refuse production (see O'Connell, Hawkes, & Jones, Reference O'Connell, Hawkes, Jones and Price1991).

Table 2.

Mean fitted probabilities with 90% credible intervals (CIs) for plant-derived, animal-derived, and inorganic materials with population and trade as predictors

Table 3.

Mean posterior probabilities with 90% CIs for artefacts containing at least one component material with a moderate or strong taphonomic signature. All are varying effect models with population as a grouping variable. Model 1 includes trade as a predictor, model 2 includes trade and all nine function variables, and model 3 includes trade and symbolism

Two artefacts caused Pareto K errors in leave-one-out (LOO) cross validation (i.e., disproportionately biased estimates). These were tyre sandals and clay pots. Clay pots aren't recorded for all populations, have a strong taphonomic signature and yet are untraded. As clay is an important material with a deep history, I chose not to exclude them. Tyre sandals are a rare clothing item that uses a traded material, has a strong taphonomic signature, and only appear in a single population (Hadza). These did represent a genuine outlier with potential to bias estimates and were excluded from the final analyses.

Although the statistics employed here are themselves sophisticated, I present fitted estimates (probabilities) in text, which can be interpreted straightforwardly by readers unfamiliar with Bayesian methods. For ease of comprehension, I report and discuss pertinent results in text. For readers who want more technical detail, a comprehensive reporting of results, including full-model estimates, model definitions, and model selection outputs, see the “Data availability” section, where commented analysis scripts and tabulated study data can also be found.

10. Would contemporary foragers leave enduring evidence of symbolism?

Contemporary foragers are just as cognitively sophisticated as any other contemporary population and the three groups in this study each have complex cosmologies, myths, norms, oral histories, and fully recursive, syntactically and phonetically sophisticated languages. The first aim of the study was to assess how much, if any, enduring, recognisably symbolic material evidence would be left by these contemporary human populations.

None of the study populations produce artefacts as detailed as figurines/paintings from Upper Palaeolithic Europe (e.g., Conard, Reference Conard2010; Harari et al., Reference Harari, Vandermuelen and Casanave2020; Klein, Reference Klein2017; Tattersall, Reference Tattersall2017a). Although there is rock art in Hadza territory (Mabulla, Reference Mabulla2005), in >100 years of ethnography, there are no accounts of its production (Marlowe, Reference Marlowe2010). Similarly, there are no records of painting from Mbuti, although they do produce intricately decorated bark cloth (Tanno, Reference Tanno1981; Fig. 1) and numerous plant-based pigments, dyes, and body paints (Tanno, Reference Tanno1981). There exists much ancient Kalahari rock art but, although there are records of other Kalahari foragers producing it (Solomon, Reference Solomon1997), the G//ana traditionally do not (Tanaka, Reference Tanaka1979, p. 197). Although there are accounts of ochre (or possibly Pterocarpus dye) use among the !Kung as bridal face paint (Marshall, Reference Marshall1976, pp. 276–277), and the /Xam as a leather-tanning agent (Wadley, Reference Wadley2005), a literature search yielded no records of dye use among the Hadza or G//ana. Moreover, despite the availability of bone/ivory, none of these populations produce carved bone figurines.

Burial, especially with grave goods, often features in discussions of prehistoric cognition (see, e.g., Pomeroy et al., Reference Pomeroy, Bennett, Hunt, Reynolds, Farr, Frouin and Barker2020; Sommer, Reference Sommer1999; Sterelny, Reference Sterelny2014; Wadley, Reference Wadley2021). Although, as elsewhere, death has important cosmological significance, there is little elaborate or symbolic burial. Although no descriptions of G//ana funerary practices were found (though see Wiessner, Reference Wiessner2009), there are accounts from the Hadza and Mbuti. Among both, individuals may be left in their huts, which are pulled down over them (Turnbull, Reference Turnbull1976; Woodburn, Reference Woodburn, Bloch and Perry1982). Although deep holes aren't made, Hadza individuals may also be interred in a shallow hole or natural hollow (e.g., an anteater hole), sometimes covered in sticks or soil to deter hyenas (Woodburn, Reference Woodburn, Bloch and Perry1982). Neither use extensive grave goods (Woodburn, Reference Woodburn, Bloch and Perry1982), though people may be buried with water gourds or digging sticks (Skaanes, Reference Skaanes2015; Woodburn, Reference Woodburn, Bloch and Perry1982). Possessions are alternatively shared out or discarded (Skaanes, Reference Skaanes2015; Turnbull, Reference Turnbull1976). The Hadza sometimes bury bodies facing a particular direction – facing a high mountain or the sunset (Woodburn, Reference Woodburn, Bloch and Perry1982). They may be placed on their sides or back, though there is no further ritual positioning or disarticulation (Woodburn, Reference Woodburn, Bloch and Perry1982). Neither the Hadza nor Mbuti practice funerary caching (sensu Pettitt, Reference Pettitt2018), and people are interred in the camp in which they died, which is typically abandoned. Graves are left unmarked (Woodburn, Reference Woodburn, Bloch and Perry1982). Therefore, although a full exploration of mortuary taphonomy is beyond the scope of this paper, neither the Hadza or Mbuti are likely to leave extensive evidence of symbolic nor perhaps even deliberate burial.

Although certain symbolic expressions associated with the Upper Palaeolithic do not occur, symbolic material culture is far from absent. Hadza children produce shaped, unfired clay dolls (Fig. 1) and cloth dolls of wrapped, unmodified rock or wood, whereas the Mbuti, alongside habitual pigment use, also produce elaborate bark honey containers. Each population produces musical instruments of several types (Marlowe, Reference Marlowe2010; Tanno, Reference Tanno1981), with and without traded materials. Moreover, the Hadza have traditionally produced numerous necklaces with a therapeutic purpose (Woodburn, Reference Woodburn1970). So, despite relatively small sets of artefacts (69–97) each population produces some which would constitute symbolic evidence by the strictest (Klein, Reference Klein2017) definition. Although it is conceivable that a human population might not create any material symbolic expressions, the present data do not make this case. However, when considering those artefacts that would reliably leave long-lasting evidence, a different picture emerges.

10.1 Evidence of symbolism excluding traded materials

For any study artefact, the mean estimated probability that it contained at least one archaeologically visible component was approximately one-third (mean p = 0.32, 90% highest density credible intervals [HDCI] = 0.27–0.37). This was predominantly a consequence of materials attained through trade. Items with traded components were substantially more likely to have a moderate/strong taphonomic signature (mean p = 0.82, 90% HDCI = 0.75–0.90) than those without, a mean absolute probability increase of 67 percentage points. This is because, across populations, materials attained from trade were overwhelmingly likely to be inorganic in origin (mean p = 0.66, 0.82, and 0.84, for the Hadza, Mbuti, and G//ana, respectively) and overwhelmingly unlikely to be animal byproducts. In consequence, materials attained through trade were disproportionately hard wearing and nonbiodegradable; and were often acquired for this reason.

This is important. Although nontraded materials are, by-and-large, similar to those available in Palaeolithic contexts (wood, stone, bone, leather, and plant fibre), traded materials such as refined metals, glass, and plastics are more recent. To better leverage the current datasets as a model for ancient hunter–gatherer taphonomy, it is necessary to consider preservation probabilities for artefacts without traded components.

When traded materials are excluded, the mean estimated probability of any artefact containing archaeologically visible components is universally low (mean p: Mbuti = 0.08; Hadza = 0.17, G//ana = 0.24). The majority of artefacts produced would be invisible under normal conditions of preservation. This was also broadly true of artefacts that might constitute evidence of symbolism (Table 3). Excluding the effects of trade, the mean probability of a symbolic artefact containing an archaeologically visible component was only 0.06 for the Mbuti (90% HDCI = 0.01–0.11) and 0.13 for the Hadza (90% HDCI = 0.04–0.22), though somewhat higher for the G//ana at p = 0.34 (90% HDCI = 0.11–0.56). The majority of archaeologically visible symbolic evidence was a consequence of a single material – ostrich eggshell – and to better understand these results, it is useful to consider each artefact individually.

Table 4 displays all artefacts that constitute evidence of symbolism and contain materials with a moderate/strong taphonomic signature. When those containing traded materials are excluded (Table 4.1), a total of two Hadza artefacts meet both criteria; four G//ana artefacts; and only one Mbuti artefact; seven in total. The shell fragments from the G//ana dancing rattle would be difficult to recognise as human-modified, leaving six.

Table 4.

All artefacts which constitute evidence of symbolism and contain at least one material with a moderate or strong taphonomic signature. Artefacts without traded materials first, artefacts with traded materials second

Of these six, five incorporate beads. One incorporated bone beads, whereas four incorporated ostrich eggshell, a material not in contemporary use by the Hadza. Ostrich-shell beads appear early in the African archaeological record (d'Errico et al., Reference d'Errico, Backwell, Villa, Degano, Lucejko, Bamford and Beaumont2012; McBrearty & Brooks, Reference McBrearty and Brooks2000) and are frequently cited as evidence for cognitive change in the African Late Stone Age (Klein, Reference Klein2017). However, contemporary ethnographic accounts of eggshell bead making show it to be an elaborate process, involving several discrete steps, five separate tools, and substantial time (Hitchcock, Reference Hitchcock2012). Many steps are neither obvious nor straightforward. Rather than an inevitable consequence of advanced cognition, it constitutes an ecology-bound invention (Mayer et al., Reference Mayer, Groman-Yaroslavski, Bar-Yosef, Hershkovitz, Kampen-Hasday, Vandermeersch and Weinstein-Evro2020) that can be both culturally transmitted and lost, as it has been today among the Hadza.

Nor is it inevitable that beads should be manufactured from enduring media such as eggshell, bone (Table 4.1), or marine shell (e.g., Miller, Sawchuk, Reedman, & Willoughby, Reference Miller, Sawchuk, Reedman and Willoughby2018); the Hadza traditionally produced beads from organic media including twigs, tubers, and acacia pods (Woodburn, Reference Woodburn1970) whereas the Mbuti use seeds (Tanno, Reference Tanno1981). Further, bead use is dependent on thread, traditionally made by chewing/rolling the ligament/sinew of a large animal among the Hadza (Marlowe, Reference Marlowe2010, p. 85) and G//ana (Hitchcock, Reference Hitchcock2012) or weaving plant fibre as among the Mbuti (Tanno, Reference Tanno1981). Thread making is another complex multistep process that can be culturally transmitted, and lost. Despite its deep history (d'Errico et al., Reference d'Errico, Backwell, Villa, Degano, Lucejko, Bamford and Beaumont2012), such knowledge is neither obvious and inevitable nor inborn. Excluding beads, no G//ana or Hadza artefacts without traded components would leave long-lasting symbolic evidence.

The Mbuti would leave just one potentially enduring symbolic artefact without traded components; a ritual horn/trumpet. This may be made of elephant tusk or bongo horn but also traditionally of wood or bamboo (Kenrick, Reference Kenrick1996; Turnbull, Reference Turnbull2015). These horns are not produced in great quantities – typically one per settlement (Tanno, Reference Tanno1981; Turnbull, Reference Turnbull2015). They are neither elaborately decorated (Turnbull, Reference Turnbull2015) nor heavily modified and may not be recognisably manmade. Moreover, although no sources provided detailed description, it is probable that where bongo horns are used, it is the biodegradable keratin sheath, not the inner bone. The phonic properties of the horn are more important than its component materials (Turnbull, Reference Turnbull2015) and wood is used more often than horn (Kenrick, Reference Kenrick1996). All else is perishable.

Each study population is the beneficiary of millennia of additional cumulative technological evolution (see d'Errico et al., Reference d'Errico, Backwell, Villa, Degano, Lucejko, Bamford and Beaumont2012; Marlowe, Apicella, & Reed, Reference Marlowe, Apicella and Reed2005) alongside technological exchange with neighbouring populations (Nurse, Reference Nurse1972; Tanno, Reference Tanno1981). Despite this, under normal conditions of preservation, certain criteria to identify cognitive modernity in the archaeological record (Klein, Reference Klein2017; Mithen, Reference Mithen, Hatfield and Pittman2013) would probably disqualify the Mbuti. Discounting shell and bone beads, which are commonly alternatively manufactured from perishable media, the Hadza and G//ana would also represent a false negative. Some have dismissed the notion that symbolic activities “might have been expressed… in non-enduring material without having been expressed in stone and bone” (Mithen, Reference Mithen, Hatfield and Pittman2013, p. 223). The present results demonstrate that this can and does happen.

10.2 Could the exclusion of traded materials mask enduring evidence of symbolism?

This discussion has so far ignored symbolic artefacts containing traded components (Table 4.2) because most materials attained from trade were not available in the deep past yet are overwhelmingly inorganic, hard wearing, and long-lasting (Fig. 2). Preservation probabilities for symbolic artefacts with traded components where 0.71 (90% HDCI = 0.5–0.94), 0.74 (90% HDCI = 0.61–0.88), and 0.94 (90% HDCI 0.87–1) for the Mbuti, Hadza, and G//ana, respectively. Although there is good reason for excluding them, their exclusion may mask symbolic artefacts that would otherwise include widely available yet enduring media such as stone and bone. For example, many artefacts that previously incorporated flaked or worked stone (e.g., knives; spearheads; axes) now incorporate metals instead (Tanaka, Reference Tanaka1979). It is useful to consider these case by case. To that end, I list all “symbolic” artefacts containing taphonomically visible traded materials in Table 4.2 and discuss each here.

Figure 2.

Bar plots showing fitted mean probabilities and 90% CIs for each of the three study populations of using animal-derived, inorganic, and plant-derived tool components. Untraded components above, traded components below.

Iron arrowheads are used by all study populations. Were iron not available, it is possible to manufacture arrowheads from stone instead (see O'Driscoll & Thompson, Reference O'Driscoll and Thompson2018). However, arrows are also manufactured entirely using perishable media. Bows are not used by all contemporary hunter–gatherers (see Stibbard-Hawkes, Reference Stibbard-Hawkes and Moreau2020, for a review) and, once again, constitute a complex technological innovation that is not universal.

The majority of other artefacts in Table 4.2, especially from the Hadza, contain glass beads. Although beads are often manufactured from enduring materials such as shell, they are also commonly manufactured from perishable media, including twigs and seeds. The Hadza and the G//ana historically also wore traded metal jewellery (brass/iron earrings, rings, bracelets) though there are no further records of rings or earrings being manufactured from nontraded materials. Bracelets are alternatively manufactured from leather or fur by two study populations though, again, not from any long-lasting materials.

The Hadza manufacture cloth children's dolls (Woodburn, Reference Woodburn1970), which sometimes incorporate cloth-wrapped rocks. However, the rocks are largely unmodified so not recognisable as human artefacts without their cloth covers. Moreover, they are alternatively made with wood.

The remaining artefacts in Table 4.2 are either instruments or incorporate metal bells. Bells are manufactured by the Mbuti from wood though no records of nontraded bells exist for the two other populations. The G//ana manufacture rattles with eggshell fragments and the Hadza using seeds, which are perishable. Finger pianos are not made without metal, and are probably cultural borrowings (Tanno, Reference Tanno1981), as are most wire string instruments (Nurse, Reference Nurse1972; but see Padilla-Iglesias et al., Reference Padilla-Iglesias, Blanco-Portillo, Ioannidis, Manica, Vinicius and Migliano2022). There is no record of string instruments being produced from nontraded materials, although there are reports of Hadza hunting bows, manufactured from wood and sinew, being played as instruments (Woodburn, Reference Woodburn1970).

Thus, although traded materials, including metals, have replaced traditional media such as bone and stone in several of the artefacts in the present sample, it is usually in tools used in foraging, manufacture, and food processing, and not items with a symbolic function. Alternatives to traded media are largely organic and ephemeral. Moreover, those alternatives which are not ephemeral are often ecologically bounded (ostrich eggshell; marine shell) and/or difficult to work with.

11. Is there population-level variability independent of differences in cognitive capacity?

Several authors (Haidle, Reference Haidle, Haidle, Conard and Bolus2016; Hopkinson, Reference Hopkinson, Roberts and Vander Linden2011; Scerri & Will, Reference Scerri and Will2023; Shea, Reference Shea2011b) have argued that interpopulation behavioural variability and ecological flexibility, rather than cognitive change, are sufficient to explain many differences in past material culture. Many highlight that population-level differences in artefactual records are rational responses to varying subsistence environments (see Collard et al., Reference Collard, Buchanan, Morin and Costopoulos2011; O'Connell, Reference O'Connell1995; Shea, Reference Shea2011a). Thus, the second aim of the study was to investigate potential sources of variation in material use and preservation probability, causally independent of capacity. Results highlight several: ecology, mobility, cultural evolution.

First, there is clear statistical evidence for population-level differences in material selection. Although all made comparable use of inorganic materials, when traded materials were excluded, the Mbuti used substantially more plant-derived materials and fewer animal-derived materials than the Hadza and G//ana (Table 2). These differences were statistically real and large (Fig. 2). Although some variation results from culturally acquired knowledge, much is probably a consequence of material availability. The Mbuti inhabit equatorial rainforest (Tanno, Reference Tanno1981), where plant-derived materials are abundant. Ecological differences are often invoked to account for differences in prehistoric material culture (see, e.g., Blinkhorn, Timbrell, Grove, & Scerri, Reference Blinkhorn, Timbrell, Grove and Scerri2022; Brumm, Reference Brumm2010; Scerri, Roberts, Yoshi Maezumi, & Malhi, Reference Scerri, Roberts, Yoshi Maezumi and Malhi2022). The present findings highlight the primacy of ecology in shaping the material record.

The Hadza and G//ana both traditionally occupy savannah bushland (Blurton Jones, Reference Blurton Jones2016; Tanaka, Reference Tanaka1979) and it is unsurprising that both were more similar to each other in material use than to the Mbuti. Hadza artefacts had a higher mean probability of incorporating plant-derived materials than G//ana artefacts and a lower mean probability of incorporating animal-derived materials. Although there was significant overlap between population distributions (Fig. 2), it was more plausible that data were created by different material selection processes than identical ones. This may, again, result from material availability. However, as many artefacts recorded only among the G//ana (e.g., feather balls; noisemakers; fire fans; straws; snares) are made from materials used by the Hadza, and vice versa (e.g., gambling chips; skipping ropes; clay dolls), knowledge transmission probably has substantial influence.

There are additional processes which probably also impact material selection, but couldn't be statistically investigated here. Cultural evolutionary dynamics including demography (see Powell et al., Reference Powell, Shennan and Thomas2009), population history (see Gray & Watts, Reference Gray and Watts2017), network structures (Sterelny, Reference Sterelny2021a), cultural exchange (sensu Granito, Tehrani, Kendal, & Scott-Phillips, Reference Granito, Tehrani, Kendal and Scott-Phillips2019), and cumulative innovation (Dean, Vale, Laland, Flynn, & Kendal, Reference Dean, Vale, Laland, Flynn and Kendal2014) probably play an important role. Residential movement also appears significant. All populations in this study are/were traditionally residentially mobile, although the Hadza more so than the G//ana (Cashdan, Reference Cashdan1984). Mobility limits the number of artefacts that may be easily transported and creates trade-offs in material selection (Tanaka, Reference Tanaka1979, p. 197). The most enduring naturally occurring materials, stone and bone, are among the densest and heaviest so will be preferred only when their utility compensates for their weight. Consequently sedentary populations, for example, those exploiting perennially available aquatic resources (Jeffery & Lahr, Reference Jeffery, Lahr and Moreau2020; Singh & Glowacki, Reference Singh and Glowacki2022), or occupying productive, defensible, or well-situated locations such as shelters (Langley et al., Reference Langley, Clarkson and Ulm2011), may be overrepresented in the archaeological record by dint of relaxed constraints on material selection. As the three populations considered here were each highly mobile, present data are insufficient to test this hypothesis directly. Other authors have investigated ecological determinants of forager toolkit complexity and repertoire size (Collard et al., Reference Collard, Kemery and Banks2005, Reference Collard, Buchanan, Morin and Costopoulos2011; Shott, Reference Shott1986; Torrence, Reference Torrence and Bailey1983) though further research would be valuable to explore the impact of mobility specifically on material selection.

12. Does artefact function influence preservation probability?

Earlier evidence is often taken to imply earlier invention. For instance tools used in butchery and food processing (Lemorini et al., Reference Lemorini, Plummer, Braun, Crittenden, Ditchfield, Bishop and Potts2014) substantially predate artwork and personal adornment in the archaeological record. However, where there are differences in artefact preservation probability, the more enduring artefact will probabilistically yield earlier evidence, even where both are of similar antiquity. Less enduring artefact types will also be more “prone to flickering” (Scerri & Will, Reference Scerri and Will2023). Thus, if artefact function influences preservation probability, it may systematically confound the relationship between antiquity of evidence and chronology of invention.

The present dataset afforded an opportunity to explore, directly, the influence of artefact function on preservation. Here, tool function substantially influenced the likelihood of tools containing enduring components. Although estimates were wide, these trends were statistically real and models including tool function substantially outperformed those without in a LOO model selection (see the “Data availability” section).

As before, for artefacts including traded components, the probability of having a moderate/strong taphonomic signature was universally high for all artefact function categories except clothing. Distributions were wide for certain categories (e.g., furniture/shelter) reflecting a category-specific paucity of information (e.g., few types of furniture/shelter incorporated traded components). There was substantial overlap in estimates among populations. Excluding traded components, most artefact types had very low probabilities of containing components with moderate/strong taphonomic signatures. Clothing was the least likely to contain enduring components, with population means centring on p = 0.01–0.02 (Table 3). Tools used for storage and transport, items of furniture/shelter, articles of play and leisure, foraging tools, and grooming/hygiene tools each also had constantly low probabilities of containing enduring materials.

Only two artefact types – artefacts used in cooking/food consumption, and tools used in raw-material preparation or tool manufacture – had probabilities of containing enduring components above 0.1 across populations. This suggests that such utilitarian tools should be overrepresented in archaeological assemblages (as indeed they often are, see Lemorini et al., Reference Lemorini, Plummer, Braun, Crittenden, Ditchfield, Bishop and Potts2014), and should have an earlier occurrence in the archaeological record (as indeed they do, see Harmand et al., Reference Harmand, Lewis, Feibel, Lepre, Prat, Lenoble and Roche2015). As before, preservation probabilities were higher for Hadza and G//ana artefacts than Mbuti artefacts.

Despite wide estimates, for two of the three populations, ritual/ornamental artefacts were more likely to contain enduring materials than other artefact types. This trend did not apply to the Mbuti and was, again, primarily a consequence of ostrich eggshell in Hadza and G//ana jewellery. This population difference in preservation probability, resulting from a single material, once again highlights that the sudden appearance of evidence for personal adornment in the African archaeological record (Klein, Reference Klein2017; Sehasseh et al., Reference Sehasseh, Fernandez, Kuhn, Stiner, Mentzer, Colarossi and Longet2021) may simply indicate shifting material preferences (e.g., ochre/marine shell/eggshell), rather than underlying differences in cognition or any more profound technological change.

13. Alternatives to evolutionary change

The data presented here show that fully modern human populations do not inevitably create extensive or, indeed, any identifiably symbolic material culture from enduring media. The results demonstrate that such items are not a prerequisite for cognitive modernity and highlight the risks of interpreting certain artefacts – figurines, artwork, beads, and pigments (Brumm et al., Reference Brumm, Oktaviana, Burhan, Hakim, Lebe, Zhao and Aubert2021; Coolidge et al., Reference Coolidge, Wynn, Overmann, Alloway and Alloway2012; d'Errico et al., Reference d'Errico, Backwell, Villa, Degano, Lucejko, Bamford and Beaumont2012; Klein, Reference Klein2017; Wadley, Reference Wadley, Haidle, Conard and Bolus2016; Watts et al., Reference Watts, Chazan and Wilkins2016) – as indicators of evolutionary change. Beyond considering shifting material preference, this discussion has not comprehensively addressed why such technologies were absent for most of our lineage's prehistory, then rapidly appeared and proliferated. This is because, although present data demonstrate the difficulties of inference from absent evidence, they provide fewer concrete answers. Moreover, the issue is complex, and better addressed elsewhere (Scerri & Will, Reference Scerri and Will2023). Yet several mechanisms merit brief consideration.

Changing mobility patterns provide one plausible alternative (Shott, Reference Shott1986; but see Collard et al., Reference Collard, Buchanan, Morin and Costopoulos2011). It is notable that many of those ethnographically documented hunter–gatherers who produce extensive symbolic material culture are sedentary or semisedentary populations, who store seasonally abundant resources such as acorns, or anadromous fish (Kelly, Reference Kelly2013; Testart et al., Reference Testart, Forbis, Hayden, Ingold, Perlman, Pokotylo and Stuart1982). Similarly, mobility and shelter have been highlighted as a potential explanation for the relative paucity of the early symbolic material record in parts of the Australian continent (Balme et al., Reference Balme, Davidson, McDonald, Stern and Veth2009; Langley et al., Reference Langley, Clarkson and Ulm2011).

Relatedly, population density might play a causal role in technological change (Collard et al., Reference Collard, Kemery and Banks2005; Kline & Boyd, Reference Kline and Boyd2010; Powell et al., Reference Powell, Shennan and Thomas2009). Larger (Powell et al., Reference Powell, Shennan and Thomas2009) or more interconnected (Sterelny, Reference Sterelny2020, Reference Sterelny2021a) populations may decrease the risk of stochastic knowledge loss. Such mechanisms could explain the small toolkit of indigenous Tasmanians (Henrich, Reference Henrich2004; Sterelny, Reference Sterelny2021a). Moreover, more innovators and denser social networks may also hasten innovation and information spread (Kline & Boyd, Reference Kline and Boyd2010). This idea has been debated (d'Errico & Henshilwood, Reference d'Errico, Henshilwood, Henshilwood and d'Errico2011; Henrich et al., Reference Henrich, Boyd, Derex, Kline, Mesoudi, Muthukrishna and Thomas2016), but may account for the patterning of prehistoric material culture in some contexts.

Yet the most straightforward and parsimonious alternative mechanism for prehistoric technological change is simple, mosaic cumulative culture (e.g., Dean et al., Reference Dean, Vale, Laland, Flynn and Kendal2014; Tennie, Call, & Tomasello, Reference Tennie, Call and Tomasello2009) alongside technological ratchets (Lombard, Reference Lombard, Haidle, Conard and Bolus2016; Tennie et al., Reference Tennie, Call and Tomasello2009). All contemporary technologies, from laptops to eating utensils, have been invented by cognitively modern humans. These technologies replicate and spread between minds through numerous cultural processes, which have been fruitfully mapped and modelled. Certain technologies may act as prerequisites, scaffolds, or even selective forces for further innovation (Sterelny, Reference Sterelny2017; Sterelny & Hiscock, Reference Sterelny and Hiscock2024). Just as writing systems enabled the encoding and storage of knowledge in stone, papyrus, and vellum, so too may the development of string have allowed innovations in bead making. Innovations in the properties of certain iron oxides may precipitate painting; innovations in stone-working techniques may enable the creation of figurines. Certain innovations may require a critical mass before a specific tipping point is reached (Scerri & Will, Reference Scerri and Will2023), giving the false impression of a revolution in cognitive capacity, but in no cases need these innovations necessitate genetic or somatic change. As this study highlights, it is not only possible, but probable that many antecedent technologies will leave little trace.

14. Purely cultural accounts of cognitive modernity

Many highlight the primacy of cultural evolutionary processes in cognitive change, and separate cognition from genetic evolution. For example, some (Sterelny, Reference Sterelny2016; Tattersall, Reference Tattersall2017b), though not all (Klein, Reference Klein2017) late/recent language origin models view language as a cultural innovation, which enables new modes of thought and artistic expression. Some view “behavioural modernity” as grounded in extragenetic innovation (Sterelny, Reference Sterelny2017, Reference Sterelny2019) in the scaffolds of thought (e.g., Sterelny, Reference Sterelny2019; Sutton, Reference Sutton and Hodder2020); tools of labour organisation (Sterelny, Reference Sterelny2017) and memory (Sterelny, Reference Sterelny2019; Sutton, Reference Sutton and Hodder2020; Tribble & Keene, Reference Tribble, Keene, Tribble and Keene2011). Here, the mind is seen as “extended” (Clark, Reference Clark, Beynon, Nehaniv and Dautenhahn2001; Sterelny, Reference Sterelny2017, Reference Sterelny2019; Sutton, Reference Sutton and Hodder2020; Wynn, Overmann, & Malafouris, Reference Wynn, Overmann and Malafouris2021) through social cognition and material technologies – “maps, signs, trail markers, scripts, notation systems, labels, instruments” (Sterelny, Reference Sterelny2017, p. 242) – allowing for definitions of cognitive sophistication that make no strong claims about innate capacities (Sterelny, Reference Sterelny2011, Reference Sterelny2016, Reference Sterelny2019). These models sidestep a host of inferential difficulties (Shea, Reference Shea2011b; Speth, Reference Speth2004), chronological complications (Scerri & Will, Reference Scerri and Will2023; Sterelny, Reference Sterelny2014), and apparent material-somatic mismatches (Sterelny, Reference Sterelny2021a) inherent in linking material change to the substrates of the brain. However, in inferring certain capacities from absence-to-presence shifts in the material record (Sterelny, Reference Sterelny2011, Reference Sterelny2016), and in coopting the terminology of earlier models (Sterelny, Reference Sterelny2011), cultural accounts sometimes share difficulties with their antecedents.

Many cultural-evolution models still often leverage absence–presence shifts in the archaeological record of certain artefacts to infer the presence or absence of other capacities (Bolhuis et al., Reference Bolhuis, Tattersall, Chomsky and Berwick2014; Sterelny, Reference Sterelny2011, Reference Sterelny2016, Reference Sterelny2014, Reference Sterelny2017; Tattersall, Reference Tattersall2017a; Tennie, Premo, Braun, & McPherron, Reference Tennie, Premo, Braun and McPherron2017) including behavioural modernity (Sterelny, Reference Sterelny2011, Reference Sterelny2014), full language (Sterelny, Reference Sterelny2016; Tattersall, Reference Tattersall2017b) or complex social organisation, and economic life (Sterelny, Reference Sterelny2014, Reference Sterelny2020, Reference Sterelny2021a). “Zone of latent solutions” models, for instance, view technological change in terms of probabilistic processes such as innovation and transmission (Tennie et al., Reference Tennie, Premo, Braun and McPherron2017) but make second-order claims about the intrinsic capacities of extinct humans (see Sterelny, Reference Sterelny2020; Sterelny & Hiscock, Reference Sterelny and Hiscock2024). Even frameworks that infer one culturally acquired skillset through indirect evidence from another may encounter problems. For example, Sterelny (Reference Sterelny2016) leveraged four categories of material evidence, including “manufacture, use, and social transmission of different technological suites” (p. 182) to infer that that H. heidelbergensis was “unlikely to have anything approximating full language” (p. 178) which probably appeared late. This paper highlights the absence of “figurines or other objects made for non-utilitarian purposes,” “jewellery,” and “ochre” (p. 179). Although Sterelny (Reference Sterelny2016) integrates three other types of information, considers perishable media, and highlights the interpretive difficulties of symbolic evidence elsewhere (e.g., Sterelny, Reference Sterelny2011, Reference Sterelny2014), he yet concludes “it is likely that we would see… traces” (p. 179). Here, the lessons of the current dataset – that living people may not create certain signs ideological life (sensu Sterelny, Reference Sterelny2014, Reference Sterelny2016), or may create them without enduring media – remain relevant.

The second set of difficulties with purely cultural accounts is not interpretive but terminological. I see two primary issues. First, although terms such as “behaviourally modern” may be used in a purely cultural sense (Sterelny, Reference Sterelny2011, Reference Sterelny2016, Reference Sterelny2019), for readers from other disciplines they risk invoking the epistemic baggage – assumptions, associations, and conclusions – of earlier models (Bar-Yosef, Reference Bar-Yosef2002; Klein, Reference Klein2002; Mellars, Reference Mellars2005, Reference Mellars2006), especially as the term “modern” retains its original meaning elsewhere (Klein, Reference Klein2019). Additionally, although it is useful to consider technological and demographic tipping points (Sterelny, Reference Sterelny2019; Sterelny & Hiscock, Reference Sterelny and Hiscock2024) the term “behavioural modernity” also inherits many attendant definitional difficulties as a threshold, trait-list, or concept (Ames et al., Reference Ames, Riel-Salvatore and Collins2013; Henshilwood & Marean, Reference Henshilwood and Marean2003; Meneganzin & Currie, Reference Meneganzin and Currie2022; Scerri & Will, Reference Scerri and Will2023; Shea, Reference Shea2011b; Stringer, Reference Stringer2002). Even the word “cognition,” although usefully defined broadly (Clark, Reference Clark, Beynon, Nehaniv and Dautenhahn2001), may, to lay readers, be redolent of intrinsic capacities such as working memory (Coolidge et al., Reference Coolidge, Wynn, Overmann, Alloway and Alloway2012) or neural connectivity (Wadley, Reference Wadley2021).

Last, even accepting equal capacity, discussions of “behaviourally modern cultures” (Sterelny, Reference Sterelny2011, Reference Sterelny2014, Reference Sterelny2016), or cultural complexity (Sterelny, Reference Sterelny2021a) risk ranking or grading cultural differences. For instance, in considering that the earliest peoples of Australia must have possessed marine travel (Allen & O'Connor, Reference Allen, O'Connell, Clark, Leach and O'Connor2008; Davidson & Noble, Reference Davidson and Noble1992; Habgood & Franklin, Reference Habgood and Franklin2008), yet left relatively few enduring traces of material complexity, Sterelny (Reference Sterelny2011) suggests that “Australians ceased to be modern after they arrived” (p. 819). This example illustrates the problems with viewing material change as unidirectional and capacity bound. However, it again places technology at the fore. The ancient Australians themselves might have queried the notion they were less modern than their forebears because they lacked boats.

Even discussion of cognitive ecologies (Sutton, Reference Sutton and Hodder2020; Tribble & Keene, Reference Tribble, Keene, Tribble and Keene2011), niches (Tribble & Keene, Reference Tribble, Keene, Tribble and Keene2011), or of past peoples living “such different lives” (Sterelny, Reference Sterelny2019), may lead us to overemphasise cultural distinctions. Although technology is indisputably important, cultural boundaries are permeable and delineated more by language barriers, social network structure or exogamy rules, and other associative proscriptions than by other innovations in the scaffolds of thought. Individuals in a foraging niche (see Sutton, Reference Sutton and Hodder2020, p. 220) have no difficulty cooperating and collaborating across such boundaries, and may readily transition to other niches entirely, and back.

Theorists do recognise modern foragers as culturally complex (Sterelny, Reference Sterelny2014, Reference Sterelny2021a). Sutton (Reference Sutton and Hodder2020) cautions against orthogenetic reasoning. Henrich (Reference Henrich2004) is clear that indigenous Tasmania experienced no devolution across cultural domains (p. 203) accompanying technology loss. Moreover, terminologically choppy waters of this kind are not unique to cognitive archaeology (see, e.g., Lavi, Rudge, & Warren, Reference Lavi, Rudge and Warren2024). Yet in, for example, defining “cultural complexity” (Sterelny, Reference Sterelny2021a) in terms of either toolkits or the structure of social networks – and focussing primarily on these in considerations of certain populations (e.g., Haidle, Reference Haidle, Haidle, Conard and Bolus2016; Henrich, Reference Henrich2004; McGrew, Reference McGrew1987; Oswalt, Reference Oswalt1976; Sterelny, Reference Sterelny2021a) – we miss that small populations, with small toolkits, may yet have rich social lives, complex belief systems, and languages. In light of present evidence, there is cause for caution in advancing schema of cognitive change that would, when extended to other human populations – or their material traces – appear to create a hierarchy of culture forms, or classify some as more cognitively or behaviourally modern, complex, or otherwise differently graded than others.

15. Limitations

Although the material culture datasets analysed here are comprehensive, and represent most recorded contemporary hunter–gatherer material diversity across a whole continent, they still have important limitations.

First, the current study incorporates evidence from only three populations. Although datasets are thorough and represent two important ecologies, this study only captures a small proportion of global hunter–gatherer diversity (see Kelly, Reference Kelly2013; Lee & Daly, Reference Lee and Daly1999). These data are sufficient to demonstrate that contemporary humans do not inevitably produce enduring symbolic artefacts. However, to statistically investigate broader patterns (see, e.g., Collard et al., Reference Collard, Kemery and Banks2005, Reference Collard, Buchanan, Morin and Costopoulos2011; Shott, Reference Shott1986; Torrence, Reference Torrence and Bailey1983), a larger dataset is needed.

Second, these datasets represent a twentieth-century snapshot of material culture over at most an 80 year span. By contrast, although lacking comparable resolution, archaeological datasets represent a much larger scale of analysis. Many sites span millennia, and data are drawn from a considerably wider geographic area. It may yet be that modern humans are defined not by their universal use of enduring symbolic material culture, but by their propensity to probabilistically reinvent it, either because of some intrinsic (Klein, Reference Klein2019) or context-bound (Henshilwood & Dubreuil, Reference Henshilwood and Dubreuil2011) proclivity, or because it exists within a particular species' zone of latent solutions (see discussion by Sterelny, Reference Sterelny2020; Sterelny & Hiscock, Reference Sterelny and Hiscock2024; Tennie et al., Reference Tennie, Braun, Premo, McPherron, Haidle, Conard and Bolus2016, Reference Tennie, Premo, Braun and McPherron2017). Under this assumption, even were evidence for symbolism often absent, general cross-site temporal trends may still track species-level cognitive change.

This assumption, although logical, is unproven, difficult to test empirically, and does not reflect historically recorded patterns of human technological evolution. Moreover, there are indications that extensive enduring symbolic evidence is not inevitable, even at greater timescales. The paucity, relative to the European record, of well-preserved early symbolic evidence from Wallacea and Sahul (but see Langley, Clarkson, & Ulm, Reference Langley, Clarkson and Ulm2019) despite at least 50,000–55,000 years of continuous modern human occupation (Brumm & Moore, Reference Brumm and Moore2005; Habgood & Franklin, Reference Habgood and Franklin2008; O'Connell et al., Reference O'Connell, Allen, Williams, Williams, Turney, Spooner and Cooper2018), probably “mainly reflects the failure of early cultural expressions to be preserved and discovered” (Hiscock, Reference Hiscock2007, p. 121) and results from the fact that “much of the ornamentation used by Australian Aboriginal people was made from perishable material” (Balme et al., Reference Balme, Davidson, McDonald, Stern and Veth2009, p. 65). This argument is not unassailable as there is increasing evidence of long-distance shell transport, ochre use, and potentially ancient artwork (David et al., Reference David, Geneste, Petchey, Delannoy, Barker and Eccleston2013; Langley et al., Reference Langley, Clarkson and Ulm2011, Reference Langley, Clarkson and Ulm2019). Yet, extragenetic processes of cultural evolution – invention, horizontal/vertical transmission, and cumulative change (e.g., Dean et al., Reference Dean, Vale, Laland, Flynn and Kendal2014; Tennie et al., Reference Tennie, Call and Tomasello2009) – still appear more parsimonious than models invoking some capacity shift or major cognitive sea change. Unfortunately, the present evidence, being narrowly bounded in time, cannot conclusively address this question.