Jagiello et al. pose a welcome and important question that cultural evolution research has yet to realistically answer: What causes “some traits to change within a few generations while others retain their form and stability for millennia”? (target article, sect. 1, para. 1). The authors offer some compelling but only partial answers: Their metaphorical bifocals are constrained by some tunnel vision.

One aspect of this is the exclusive focus on human culture. In recent decades, the transmission of cultural practices across populations and generations has been documented in mammals, birds, fish, and insects, as well as many different domains of behaviour, from tool use to vocal repertoires (Allen, Reference Allen2019; Aplin, Reference Aplin2019; Whitehead & Rendell, Reference Whitehead and Rendell2015; Whiten, Reference Whiten2021). As in humans, at least one sex disperses at maturity, avoiding incest, so when an animal possesses cultural knowledge lacking in the community it enters, the contrast quoted above is in play. Will the individual display and thus potentially spread the cultural innovation concerned, or will it instead conform to existing local customs? And why the difference? In chimpanzees for example, cultural transmission may occur, as in the between-community spread of using a fine probe to fish ants from under tree bark (O'Malley, Wallauer, Murray, & Goodall, Reference O'Malley, Wallauer, Murray and Goodall2012), whereas in other cases conformity overrides this, as when female immigrants to new communities adopt local ways of using natural hammers to crack nuts (Luncz & Boesch, Reference Luncz and Boesch2014).

Jagiello et al. assert in their abstract that “studies of cultural learning have tended to prioritize instrumental learning … over conformism and the preservation of conventions.” But recent research has revealed that conformity is widespread in animal cultural transmission – one of several adaptive biases in social learning (Kendal et al., Reference Kendal, Boogert, Rendell, Laland, Webster and Jones2018). In a recent review (Whiten, Reference Whiten2019a) I distinguish three main forms of conformity, the most basic being copying majority preferences in one's social world. A second, more intense manifestation is “conformist bias,” in which an individual witnessing a certain majority (e.g., 70%) preference for some behavioural option displays an exaggerated disposition to adopt it (e.g., 90%). The other intense kind of conformity I labelled “Aschian conformity” which involves an individual abandoning their existing preference or behaviour in favour of an alternative observed in a majority of others. In chimpanzees we have evidence for both the first (Haun, Rekers, & Tomasello, Reference Haun, Rekers and Tomasello2012) and third of these (Watson, Lambeth, Schapiro, & Whiten, Reference Watson, Lambeth, Schapiro and Whiten2018) – and not only in apes (Aplin et al., Reference Aplin, Farine, Morand-Ferron, Cockburn, Thornton and Sheldon2015). Identifying the second type requires large populations but we have such evidence for birds (Aplin et al., Reference Aplin, Farine, Morand-Ferron, Cockburn, Thornton and Sheldon2015) and insects (Danchin et al., Reference Danchin, Nöbel, Pocheville, Dagaeff, Demay, Alphand and Isabel2018).

All have been identified in humans of course. My point is that the very particular focus of Jagiello et al. on ritual as a context for conformity neglects the probability that such phenomena likely did not arise out of the blue but instead built on phenomena widespread in our species' evolutionary past. Social psychologists distinguish prescriptive (or injunctive) conformity from descriptive (or statistical) conformity (Lapinsky & Rimal, Reference Lapinsky and Rimal2005). It is the former on which Jagiello et al. focus (“one should do X”). We have yet to see compelling evidence for this in nonhuman species: The forms of conformity in nonhumans outlined above seem consistent with merely statistical conformity. However, Eriksson, Strimling, and Coultas (Reference Eriksson, Strimling and Coultas2015) showed that people readily generate injunctive norms from observation of mere statistical majorities among their companions. A corresponding process may plausibly have occurred on organic or cultural evolutionary timescales.

There is a further potential parallel in animal culture concerning the distinction that Jagiello et al. focus on, between conformity (and over-imitation) serving informational versus social-integrative functions (Deutsch & Gerard, Reference Deutsch and Gerard1955). For example in a field experiment with wild vervet monkeys, van de Waal, Borgeaud, and Whiten (Reference van de Waal, Borgeaud and Whiten2013) found that 9/10 maturing males who had lived in groups that had learned to eat just one of two coloured provisioned foods quickly conformed to the opposite preference they witnessed on migrating to a new group. An informational function might be that the local monkeys know the best local choices so they should be copied; an alternative socio-integrative hypothesis is that by acting like the locals, incomers will be accepted the sooner. Experiments have shown that a person who imitates a monkey is later likely to elicit more affiliative responses than another who does not imitate it (Paukner, Suomi, Visalberghi, & Ferrari, Reference Paukner, Suomi, Visalberghi and Ferrari2009). That the one vervet male who did not conform had quickly dominated their adopted group is consistent with the social function hypothesis, because he did not need to ingratiate himself (see also van de Waal, van Schaik, & Whiten, Reference van de Waal, van Schaik and Whiten2017).

Another narrowness in the approach of Jagiello is advocating a dichotomy between “technological innovation” and “non-instrumental learning,” linking in Box 1 with a dichotomy between “instrumental stance” and “ritual stance.” I question whether this dichotomy accommodates all human and nonhuman cultural phenomena. Where, for example, do human languages fit – or indeed other forms of cultural communication such as bird and whale song? Birdsong can include elements that are stable over decades (“recurrent fidelity” in Heyes' (Reference Heyes2018) terms) plus other elements that evolve across years (Whiten, Reference Whiten2019b; Williams, Levin, Norris, Newman, & Wheelwright, Reference Williams, Levin, Norris, Newman and Wheelwright2013). Humpback whale songs evolve greater complexity over several years, but may then be replaced by new songs, to which all whales in the population conform, with this new song then being transmitted to populations across ocean basin scales (Allen, Garland, Dunlop, & Noad, Reference Allen, Garland, Dunlop and Noad2018).

Linked questions concern the scope of “convention” (Box 1): Presumably our linguistic lexicons are prime examples of conventions – so what then of bird and whale songs, given that both express local arbitrary dialects that function in the population concerned (“coordination devices,” Box 1), but not in others, where they can, for example, prevent interbreeding because they lack requisite meaning for the females there (Grant & Grant, Reference Grant and Grant2002). Going beyond vocal communication, van Leeuwen, Cronin, and Haun (Reference van Leeuwen, Cronin and Haun2014) reported that a female chimpanzee's innovation of arranging a grass leaf in one ear was adopted by most of her group. Where (if at all) might such phenomena fit in the schemes (e.g., Fig. 3) of Jagiello et al.?