Evolution and the human family How families have evolved

Rissa de la Paz: Welcome to Darwin Now. In this podcast, we’ll be looking at how evolutionary biology can shed light on aspects of human behaviour. We’ve already seen how in the rest of the natural world, evolution is often the result of a trade-off between competing demands for major tasks such as growth, development and reproduction. Can something as seemingly complex as human life history or even the origins of family and social systems also be looked at in terms of evolutionary trade-offs? Ruth Mace, Professor of Evolutionary at University College London, applies just such an approach in her study of diverse human populations. She explains what motivated her to shift her own research focus from animal to human subjects.

Ruth Mace: I trained originally as a behavioural ecologist, which is someone who tries to understand how evolution has shaped behaviour to respond to different environments. And it always occurred to me that it could be a very useful framework for trying to understand human behaviour, which includes culture because so much of human behaviour is culturally learned, so it seemed to me to be a very natural step.

Rissa: What are the challenges of studying the evolution of human behaviour?

Ruth: Well obviously one of the difficulties about studying human behaviour compared to animal behaviour is that you can’t do experiments on humans, you can’t manipulate their reproductive success or things that might influence how they survive. But then there are also all sorts of advantages, not least that people can talk and people can keep written records about themselves, so you might be able to interview someone about their birth history and find out exactly how many children they’ve had over the last 25 years, how many of them died, and you can only get that kind of data from a red deer or primate if you watch them every year for 25 years.

You may also find the data just in records, so people keep legal records, they keep demographic records, they keep medical records, and all these sources are now being potentially exploited to find really quite useful information

Rissa: For Mace and her colleagues, key questions about human family organisation - when to begin reproducing as a woman, how to choose a mate or how much to invest in your children – can be studied fruitfully through the lens of evolutionary biology. And this can have broader cultural implications.

Ruth: Nearly all human behaviour is at least to some extent learnt from others so it’s cultural to some extent, and that’s led some people to think that and evolution are really not useful concepts. But first of all, an awful lot of what we do is clearly influenced by exactly what you would predict from natural selective theory. So for example, people devote most of their energy throughout their lives to raising a family, looking after their children, seeking mates, all these things are direct predictions from natural selection.

When cultural institutions try to enforce rules that don’t allow people to do those things people don’t accept those cultural institutions. And in fact really the cultural institutions are more likely to be designed to create some kind of social norm which helps us do those things in whatever environment we’re living in.

And the other thing to say is that cultural traits, even if not subject to natural selection, could be undergoing a process of in that they are transmitted from one individual to another, and cultural traits that have properties that make them very successful about being transmitted are going to spread. And in fact in the final chapter of The Selfish Gene talks about the spread of cultural traits and how that also has evolutionary properties.