Boyd et al. (Reference Boyd, Richerson and Henrich2011) created a divide between the “cognitive niche hypothesis” (e.g., Barrett et al. Reference Barrett, Cosmides, Tooby, Gangestad and Simpson2007; Pinker Reference Pinker2010) and the “cultural niche hypothesis.” They define the cognitive niche in terms of evolutionary psychology as studied by Cosmides and Tooby (Reference Cosmides, Tooby, Sternberg and Kaufman2001) and their followers. In our view, this delimitation amounts to a very restricted account of cognition. Thus, we agree with Osiurak and Reynaud (O&R) that research concerning the so-called cultural niche has a strong tendency to ignore technical reasoning skills. In this respect, we also see the elephant in the room.

However, O&R do not account for the evolutionary emergence and development of “the elephant.” In section 2.2.1., paragraph 1, they write that “CTC emerges in humans because we possess the ‘dormant’ technical potential” that other animals do not have, but they provide no explanation of how this dormant potential has arisen (with tongue in cheek we remind the authors of the “virtus dormitiva” in Molière's Le Malade imaginaire). Here, we provide a discussion on two topics that we see may help explain where the elephant comes from.

First, there is a tight correlation between the evolution of cumulative technological culture (CTC) and the evolution of causal cognition. We regret that O&R (footnote 4) use the term “technical cognition” instead of “causal cognition,” which is more common and more accurate for the topics they consider. There is co-evolution between technical engagement in the manufacturing and use of tools, and advanced forms of causal cognition in the human lineage. Human causal thinking has become detached from space and time, so that instead of just reacting to perceptual input, our minds can simulate actions and forces and their causal consequences. Unlike the situation for other primate species, an increasing emphasis on technical engagement made some hominins capable of reasoning about causal processes, for example, forces involved in tool use (Gärdenfors & Lombard Reference Gärdenfors and Lombard2018). Tools extend the action field and action control of the users (Arbib et al. Reference Arbib, Bonaiuto, Jacobs and Frey2009). Because even the reactive fields of hand neurons are extended to the hand together with the tool, the use of tools is assimilated not only into the body schema, but also into neural circuits that effect cognition (Bruner & Lozano Ruiz Reference Bruner and Lozano Ruiz2014; Maravita & Iriki Reference Maravita and Iriki2004). Thus, the way we think is profoundly rooted in and shaped by technical engagement. As an extension of these mechanisms, human causal cognition has evolved to become detached from what is present here and now, so that instead of simply reacting to perceptual input, our minds can simulate actions and forces and their causal consequences (Gärdenfors & Lombard Reference Gärdenfors and Lombard2018; Penn & Povinelli Reference Penn and Povinelli2007). Such understanding of forces forms the core of what O&R call technical-reasoning skills. Furthermore, causal thinking has become increasingly dependent on having a theory of mind (Lombard & Gärdenfors Reference Lombard and Gärdenfors2017; Stuart-Fox Reference Stuart-Fox2014). In our opinion, an explanation of CTC should, at least in part, be based on the co-evolution between technical competence and causal cognition.

Second, intentional teaching plays a greater role in the evolution of CTC than acknowledged by O&R, who claim that teaching might “not be the necessary condition for CTC” (sect. 3.3, para. 4) (in line with Derex et al. Reference Derex, Bonnefon, Boyd and Mesoudi2019). Several studies, however, emphasize the importance of intentional teaching – as opposed to learning by imitation only – in cultural transmission when learning complex, cognitively opaque skills such as the making of elaborate stone tools (d'Errico & Banks Reference d'Errico and Banks2015; Gärdenfors & Högberg Reference Gärdenfors and Högberg2017). Indeed, intentional teaching is a fundamental human behavior, and from early childhood and onward humans cannot help teaching each other (Riede et al. Reference Riede, Johannsen, Högberg, Nowell and Lombard2018). Cross-cultural research underlines that it is indeed in economically and culturally highly valued domains where teaching is emphasized (Kline Reference Kline2015), so that teaching is clearly beneficial for the transmission of technical knowledge.

Teaching is not only the presence of verbal interaction as in O&R's Table 1, line 3. And there are two kinds of “observation” (Table 1, line 2): one where the learner is observing a model performing a task without directing itself to the learner. This is typically the case in chimpanzee nut-cracking (Lombard et al. Reference Lombard, Högberg and Haidle2019). The second type is where a learner is observing a teacher intentionally demonstrating or pantomiming how a tool is used or manufactured, which considerably improves the student's learning process (Gärdenfors & Högberg Reference Gärdenfors and Högberg2017). Combined with verbal explanation of the hidden forces involved in performing the task, the learner can gain deeper understanding of the process and thereby be able to generalize and innovate. This process is also strengthened by the development of more advanced forms of a theory of mind in teachers and learners.

Many animal species have highly complex social structures, yet none has become obligatory stone tool users (Shea Reference Shea2017; Zilhāo Reference Zilhāo2019), nor serial inventors and innovators of technologies as part of their survival mechanism the way humans have. For us, no separatist explanatory framework suffices for addressing “the elephant,” or as O&R put it “the increase in the efficiency and complexity of tools and techniques in human populations over generations.” Instead, it is necessary to be increasingly aware of the fact that throughout our long evolutionary history there may have been different contextual emphases on a range of push and pull factors at play.

In short, we agree with O&R that CTC is both a social and technological phenomenon. But it is our view that the techno-behaviors that evolved along hominin lines cannot be maintained without intentional teaching, making them part of a cultural niche. At the same time, we argue that there is a co-evolution between technology and more and more advanced forms of causal cognition; and that theory of mind is a critical social cognition component of the causal cognition system so that in humans the cultural niche cannot be separated from the cognitive niche. From an evolutionary perspective, O&R's assumption “that cumulative technological culture originates in non-social cognitive skills” is thus as limiting as the notion that causal understanding did not play a role in the development of culturally evolving technology (Derex et al. Reference Derex, Bonnefon, Boyd and Mesoudi2019).