Gene-culture co-evolution
As usual, read this blog, do the reading, and then take the quiz on Top Hat to test your understanding.
In this final lecture, I am going to talk about gene-culture co-evolution, and how it relates to language. The reading for this week is Chapter 7 of Laland & Brown (2011). We have multiple copies of this book in the library (make sure you get the 2011 second edition, rather than the 2002 first edition), or you can download this chapter from Learn (under Course Materials, I have put it near the top so you can find it easily).
Kevin Lala (formerly Kevin Laland) and Gillian Brown are based at St Andrews, in biology and psychology respectively; they both do fascinating work on how genes and culture interact to shape behaviour and cognition in humans and other animals. Their 2011 book provides an overview of a group of related scientific approaches (sociobiology, human behavioural ecology, evolutionary psychology, cultural evolution, gene-culture co-evolution) based on the idea that we can explain human behaviour/cognition in evolutionary terms. We are dipping in for their summary of the last of these approaches, but they do mention the others at the start of the chapter (particularly sociobiology), so I’ll describe them very briefly below to give you the flavour, and if you want to know more you can read the appropriate chapter. I’ll also flag up a couple of areas of the chapter you can skim over.
The main idea behind gene-culture coevolution is that genetic and cultural evolution interact with each other: culturally-transmitted behaviours (like farming, tool use, urban living or language) create selection pressures which drive genetic evolution, and that genetic evolution sets the scene for further cultural evolution. We already came across this idea in relation to the Morgan et al. (2015) paper on the co-evolution of language and tool use (on which Lala is an author, appearing as Laland). The idea in that paper is that the use of stone tools (a socially-learned behaviour) generated a selection pressure for enhanced language abilities (because this facilitates the learning and transmission of stone tool technologies); natural selection responded by selecting for genes which produced individuals with improved communicative abilities; the enhanced cognitive/communicative abilities produced by natural selection then set the stage for the development of more complex technologies (again via social learning), which in turn increased the selection pressure for genes encoding more sophisticated language/teaching abilities, and so on. This is a classic (hypothetical) case of gene-culture co-evolution: genetic and cultural evolution feed back on one another, each driving on changes in the other.
While this case involving language is rather speculative, there are a number of better-evidenced cases of gene-culture co-evolution summarised in the reading, including classic work on how the cultural practice of dairying generates selection pressure for genes allowing individuals to consume milk into adulthood, and how cooking might have changed selection pressures on facial musculature (basically if you cook your food you don’t need to chew it as much).
For me, the most exciting idea in this chapter is that humans have undergone rapid evolution in the recent past (and therefore probably in the present day), as a result of environments we ourselves have created through culturally-transmitted behaviours including agriculture, our social systems, and maybe language. I think a lot of people have the intuition that biological evolution is basically finished in humans, because we can insulate ourselves from the environment through culturally-transmitted skills, behaviours and technologies (this is what Lala & Brown call counteractive niche construction); but the exciting thing is that exactly the same processes generate new selection pressures, as we create new environments which our must genes adapt to (this is what Lala & Brown call inceptive niche construction).
As I mentioned above, this is the last chapter of a book looking at 5 different ways of applying evolutionary approaches to understanding human behaviour - sociobiology, human behavioural ecology, evolutionary psychology, cultural evolution, gene-culture co-evolution. These terms make a few appearances throughout this chapter - don’t worry about it too much, but here’s a very quick summary of each (and if you want more detail you’ll have to get the book from the library or a shop and read it!).
Sociobiology: Sociobiologists take a gene’s-eye view of social behaviours, and try to understand how behaviours like altruism, communication etc could be explained as products of natural selection. You have already seen (in passing) some of the key ideas from sociobiology, including kin selection and reciprocal altruism, both of which explain social behaviours in terms of natural selection. Human sociobiology applies these same ideas to humans. Human sociobiology was one of the earliest evolutionary approaches to understanding human behaviour; as you might expect, applying these same sorts of gene-centred ideas to human behaviour was rather controversial, because they tend to de-emphasise the role of learning and flexibility at the level of the individual.
Human behavioural ecology: Behavioural ecology is the study of how ecological pressures (e.g. from the environment) generate selection pressures that drive adaptation. Human behavioural ecology applies these same ideas to humans: is the variation we see in human behaviour driven by adaptive responses to different ecological conditions? Unlike human sociobiology, human behavioural ecology normally assumes that natural selection has selected for extreme flexibility in human behaviour, which allows individuals to adapt their behaviour to their ecological circumstances: in other words, evolution by natural selection is responsible for human adaptation to their environment (as a sociobiologist might also think), but at one step removed, by making humans flexible enough to adapt to their environment via learning.
Evolutionary psychology: Evolutionary psychologists assume that human cognition is a product of a suite of evolved psychological mechanisms, adaptations of the human mind produced by natural selection. Steven Pinker, whose views on language you have come across on this course, is a fairly classic evolutionary psychologist, in that he tries to provide adaptive explanations for various aspects of human cognition, including language; even within language, he takes the classic evolutionary psychology approach of carving up language into multiple component parts, and providing evolutionary explanations for each of them.
Cultural evolution: You have seen quite a lot of this in the latter part of this course, the key idea being is that socially-learned behaviours change and evolve as they are passed from person to person, and that this process of cultural evolution is important in explaining many aspects of human behaviour.
Gene-cuture co-evolution: The subject of this chapter, and in a way an attempt to combine insights from (a sensible version of) evolutionary psychology and cultural evolution.
As Lala & Brown mention, gene-culture co-evolution is a fairly technical field, and one of the central approaches to understanding how genes and culture might influence each other is to build mathematical models of how the frequencies of different genetic and cultural traits might change over time. They give a little toy example of this in the reading - hopefully this will give you the gist, but don’t worry about the details.
They spend quite a lot of time talking about group selection (the idea that groups, like genes, might be the target of natural selection - an old idea with a bad reputation that’s undergone a slight rehabilitation recently) and heritability - again, read these through for the gist, but don’t worry about the details.
Laland, K. N. & Brown, G. R. (2011). Sense and nonsense: evolutionary perspectives on human behaviour, 2nd edition. Oxford: Oxford University Press.
Morgan, T. J. H., Uomini, N. T., Rendell, L. E., Chouinard-Thuly, L., Street, S. E., Lewis, H. M., Cross, C. P., Evans, C., Kearney, R., de la Torre, I., Whiten, A. & Laland, K. N. (2015). Experimental evidence for the co-evolution of hominin tool-making teaching and language. Nature Communications, 6, 6029.
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