Week 15: Sterelny (2011) From Hominins to humans: how sapiens became behaviourally modern

This paper discusses what Colin Renfrew has labelled the “sapient paradox” – the odd time lag of approximately 100-50kya between the appearance of anatomically modern humans in the geological record and the onset of what is called “behavioural modernity“. Kim Sterelny offers a niche construction perspective on this problem to dissolve the paradox by arguing that behavioural modernity is a cultural achievement – and he emphasises the importance of [1] a suite of cognitive adaptations for cultural learning (see week 6); and [2] specialised developmental environments (see week 12).

Behavioural modernity can be identified by a set of markers (2011, pp. 810-811):

  • Complex foraging societies in a wide range of different and demanding ecological environments (e.g. fruits may give it up easily but roots are storage organs and require preparation and cultivation to make them safely edible – also see Sterelny 2012)
  • Rich technology (e.g. clothes, fire, shelters, spear throwers and other multi-part tools) and capacity to cross large bodies of water (e.g. reaching Australia)
  • Hunting dangerous animals (i.e. requires complex coordination and cooperation)
  • Use of physical symbols and artwork
  • Burial practices

Although these appear definitively from 50kya, there is plenty of evidence of most of these behaviours appearing prior to this period in Africa. Indeed, in their seminal paper Sally McBreaty & Alison Brooks (2000) demolish the notion that behavioural modernity occurred due to a genetic switch by showing that this claim relies on European data and overlooks the more important African data which shows that behavioural modernity begins patchily much earlier.

Sterelny’s answer to the origin of these capacities/features is that they have come about through a specialised developmental niche that is characterised by high fidelity and broad bandwidth transmission of cultural knowledge (tools and techniques, etc.) intergenerationally. In his book Thought in a Hostile World (2003), he emphasises the importance of these features as one of the distinguishing markers of our unique species. In particular he relates it to Michael Tomasello’s (1999) notion of a “cultural ratchet“. Here the metaphor of ratchet is intended to indicate that the retention of cultural knowledge across generations does not undergo slippage – i.e. there is a tightness and accuracy in how knowledge is carried across generations so that it is not lost. High fidelity and broad bandwidth transmission channels increase the chance of this. One putative mechanism in this is the human propensity for over-imitation – we copy the procedure not just the goal (see week 10 for a discussion).

High fidelity in copying enables the accumulation of  cultural knowledge across generations. Tomasello, Sterelny, and others (e.g. Henrich 2016) have argued that this is a distinctive feature of species – and that it is cultural achievement that properly demarcates our species success (see Boyd et al 2011). This accumulation of “cognitive capital” allowed our species to tackle problems that would defy solely de novo individual ingenuity (as the natural experiments discussed by Boyd et al nicely show).

 

The importance of group size and the dangers of collapse

Before moving on to consider the details of the niche construction model, I would like to highlight what I take to be the most important aspect – not just from a technical point of view but also from a wider ethical perspective – of this approach to the sapient paradox. Viz. behavioural modernity is a cultural achievement, not something that arose from some genetic switch. This is partly attested to by the fact traces of behavioural modernity can be found in the paleo-archaeological record before the supposed revolution. But what is distinctive of these early traces is that although they can last for long periods they eventually die out. Sterelny takes this to be distinctive of the fact that the feedback loop between cognitive adaptations and specialised developmental environment began incrementally and in a piecemeal fashion. For me, what is terrifying about this is that it particularly highlights that many of our great current achievements are not as robust as we often take them to be. A sufficient break in Tomasello’s ratchet could easily eradicate much of our cultural knowledge – and thus, what we think of as marking us out as distinctively human. There are numerous examples in the archaeological record – distant and much more proximal – which show cultures that were incredibly sophisticated but which took a hit (usually ecological) and subsequently collapsed – e.g. after the end of the Roman empire there were no structures built in Europe to match the Colosseum for nearly 1000 years until the building of Cathedrals began in the 13th century (see Jared Diamond’s book Collapse for a detailed and quite frightening account of many examples of societal collapse from across the planet – including the Norse in Greenland, Easter Island, and several empires of the Americas [a more ancient example are the Indigenous people of Tasmania – see Henrich 2016 for details]).

In most of these cases a key component for why behavioural modernity or complex societies fail to be retained or improved upon is group size. Sterelny acknowledges that his “apprentice model” which uses niche construction is supplementary to, and consilient with, an approach in the literature which emphasises the importance of “group density/population pressure models” for driving behavioural modernity. Group size is important in multiple ways. Firstly, without a sufficiently sized group one cannot afford to support specialists. Specialists are crucial for focusing on specific skills and improving them. If one’s group is insufficient in size then it is unlikely that there will be any agent with the predilection or time/energy to engage in specialisation (Sterelny 2011, p. 817). Secondly, whereas the first point relates directly to innovation and improvement, group size also relates to retention – viz. if one does not have a sufficient number of teachers and learners then it is unlikely that a skill or piece of cultural knowledge will be properly transmitted intergenerationally.

This has been nicely demonstrated recently in lab based experiments by Muthukrishna and colleagues (2014). Using a number of WEIRD participants in two groups they tested how well a culturally learnt skill was passed between ten ‘generations’. In the blue group learners could only learn from one teacher, and their performance was compared to that of learners in the red group who could learn from five teachers. The aim of the experiment was to show that if a group size is not sufficiently large enough this can lead to a degrading of a skill. And indeed whereas the red group saw a steady improvement of the skill performance across the ten generations, the blue group saw a marked decline – as can be seen in the graph below (taken from Muthukrishna et al 2014, p. 3).

muthukrishna et al

 

What does niche construction bring to the table?

This lab based experiment has been corroborated by several others conducted by this team and others (see Henrich 2016, ch12 for details). These experiments show that redundancy is an important part of what Sterelny terms the “accumulative cultural niche”. But one could ask (indeed, was asked in our group discussion) what niche construction brings to the table in dissolving the sapient paradox and understanding human cognition/culture in general? One could argue that it is an unnecessary appendage beyond emphasising the importance of culture and population pressure. Directly answering these questions, Sterelny notes that the population pressure model is subject to three criticisms (2011, p. 818):

  1. It cannot explain innovation
  2. Why was there a spreading of hominins prior to the acquisition of new skills?
  3. Perhaps most damagingly, there is no evidence in the paleo-archaeological record of an increased human population when this model requires there to have been

In contrast, Sterelny sees his emphasis on the cultural ratchet and developmental niches as explaining innovation (although see Henrich 2016 for an alternative account of how innovation can arise through group size and lucky copying errors that are improvements). And the incremental nature (as opposed to saltationist) of how this feedback loop arose also accounts for the evidence of behavioural modernity prior to 50kya. It also places an emphasis on the differences for localised populations which leads to a widely variable set of behaviours prior to the expansion of 50kya.

To conclude I list some other positive features that I think a niche construction model brings to the table:

  • The niche construction perspective brings together a wide range of different fields under one umbrella or framework for exploring human cognition, evolution and culture (see Sterelny 2003, pp. 171-173). Improving cross-dialogue between the different disciplines in these overlapping topics is crucial. [The counter-argument here is that the term ‘niche’ has been applied to widely and is now losing preciseness in how it is used thus causing confusions and papering over areas of conceptual difficulty. This is indeed a worry and one that needs to be monitored]
  • The niche construction perspective obliterates the spurious division between culture and nature that often plagues discussions in the discussion of human nature and importance of culture – it shows that human cultural behaviour and environments are a wholly natural product. And it provides us with a theoretical language to discuss this in a sensible manner [with the caveat of the above worry]
  • Niche construction emphasises the relationship between the organism and its environment – and furthermore stipulates that this is a symmetric relationship.
  • In terms of culture and cognition, niche construction provides a theoretical framework that can explicate how the two have become blurred in our species – viz. we can refer to cultural-cognitive niches in which humans develop (e.g. public languages, epistemic tools and techniques). And this provides us with a much more nuanced understanding of human cognitive capacities and how they are acquired and deployed. [albeit that one must be careful to identify phylogenetic, historical and ontogenetic time-scales clearly]
  • Cultural-cognitive niches – as sets of patterned practices – offer us a more reasonable and tractable means of discussing and investigating the differences in cognitive capacities of agents from different cultures without descending into the spurious and unhelpful East-West dichotomy (see Week 1, 2, 3 and 10 for previous discussions of this).

 

Cheers

 

Alex

 

References:

Boyd et al 2011 The cultural niche: Why social learning is essential for human adaptation. PNAS 108 (2), 10918–10925. 

Henrich 2016 The Secrets of Our Success: How culture is driving human evolution, domesticating our species, and making us smarter. Oxford: Princeton University Press.

McBreaty & Brooks 2000 The revolution that wasn’t: a new interpretation of the origin of modern human behavior. Journal of Human Evolution 39, 453-563.

Muthukrishna et al 2014 Sociality influences cultural complexity. Proceedings of the Royal Society: B 281 (1774), 2511.

Sterelny 2003 Thought in a Hostile World: The Evolution of Human Cognition. Oxford: Blackwell Publishing.

Sterelny 2011 From Hominins to humans: how sapiens became behaviourally modern. Philosophical Transactions of the Royal Society: B 366, 809-822.

Sterelny 2012 The Evolved Apprentice: How evolution made humans unique. Cambridge, MA: MIT Press.

Tomasello 1999 The Cultural Origins of Human Cognition. London: Harvard University Press.

 

Additional links:

Here is a video of Colin Renfrew discussing the sapient paradox

Here is a video of Kim Sterelny delivering a lecturer that details part of his The Evolved Apprentice.

 

 

 

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