A complex adaptive system may be essential for cumulative modifications in tool design

Abstract

The cumulative modification of tool designs over time is a crucial development for technological evolution. Cognitive-related prerequisites for this technological capability are innovative behaviour and the faithful inter-generational transmission and maintenance of tool designs by accurate social learning processes. Here, we investigated the hypothesis that a complex of morphological and behavioural adaptations specifically for tool skills is also required. In a novel analysis we compared the tool-associated adaptive patterns in Homo erectus and the New Caledonian crow. Both species provide the most convincing early Homo and nonhuman evidence, respectively, for the making of cumulatively modified tools. We identified probable shared traits in H. erectus and the New Caledonian crow that include morphological adaptations specifically for enhanced tool manipulation and a significant component of daily diet from hunting and/or processing animal food with tools. We propose that a tool-using lifestyle based on animal food that confers a reproductive advantage and evolves enhanced tool manipulation skills, together with appropriate innovative ability and social learning processes, may be essential for cumulative modification of tool designs.

The elephant in the room: What matters cognitively in cumulative technological culture

“…Although non-cultural processes are expected to contribute to shaping the technology of New Caledonian crows (Kenward et al 2005;Rutz et al 2018), we should not underestimate the extent to which this was also the case in our tool-making ancestors (e.g., Corbey et al 2016). Therefore, whatever the precise contributions of genetics, individual learning and social transmission (Hunt & Uomini 2016;Rutz et al 2018), the New Caledonian crowand other non-human tool users (e.g., Rutz et al 2016a)provide a powerful comparative framework (Dean et al 2014) for identifying the basic biological processes that enable cumulative technological evolution.…”

A theory limited in scope and evidence

“…According to a recent consensus definition (Mesoudi & Thornton 2018), the New Caledonian crow is a compelling candidate for cumulative technological culture (Hunt & Uomini 2016;St Clair et al 2018). A detailed evaluation is beyond the scope of this commentary and will be provided elsewhere, but the key points can be summarised as follows.…”

Corvid Technologies: How Do New Caledonian Crows Get Their Tool Designs?

“…These designs vary considerably in shape, size and overall complexity, with striking population differences in tool repertoires [2]. It has been suggested that this diversity results from the cultural accumulation of innovations [2,3]. This is an exciting possibility, given that such cumulative cultural evolution was once believed to be a uniquely human phenomenon [4].…”

“…Importantly, neither of these studies employed a tool-manufacture paradigm, so they could only make inferences about general, rather than toolmanufacture-specific, social-learning capacities [18]. Given these caveats, it seems premature to rule out the possibility that New Caledonian crows can learn about tool designs from watching -and interacting with -skilled demonstrators [3].…”

“…Given the diversity, complexity, and spatial distribution of their tool designs [1,2], New Caledonian crows may provide the only known non-primate example of cumulative cultural evolution of technology [3,4,19]. This makes them an exceptionally valuable model system for gaining comparative insights into the processes that shaped humans' astounding technological prowess.…”