What Evolution Really Tells Us About Sex, Diet, and How We Live
Book review by Anthony Campbell. The review is licensed under a Creative Commons Licence.
There is a widespread belief that many of our modern ills, physical and mental, result from a mismatch between our genes and the artificial environment that we have created for ourselves. Books, magazine articles, TV programmes, and numerous websites popularise the view that we were shaped over many thousands or millions of years to live a hunter-gatherer existence in small groups, yet now we live in huge cities with millions of inhabitants. In this 'unnatural' environment we encounter an abundant supply of food and drink of kinds that we are not evolutionarily adapted for. A critical point in our path to all this was the adoption of agriculture a 'mere' ten thousand years or so ago. The path to salvation lies in returning to the habits and diets of our palaeolithic ancestors.
This is an intuitively appealing story, but is it true? According to Marlene Zuk many of the assumptions on which it is based are questionable. While not rejecting the importance of evolution in shaping us—quite the opposite—Zuk picks the presuppositions of the 'paleofantasists' to pieces and shows how ill-founded many of their ideas are. In me, this prompted the thought that the current enthusiasm for life in the palaeolithic really a modern version of the myth of the Noble Savage or a secular version of the legend of the Garden of Eden.
The first problem we encounter in seeking to revert to the way of life of our remote ancestors is that much of what we think we know about that way of life (assuming there was only one version of it, which is unlikely) is based on guesswork. True, we can infer a surprising amount these days from archaeology, thanks to advances in technique, and there is also valuable information to be deduced from genetics, but there will always remain vast areas of ignorance. In an attempt to fill in some of the gaps, people often look to the habits of chimpanzees, our closest living relatives. Another potential source of information is studies of the (very few) surviving hunter-gatherer societies, but it is doubtful that that any of these societies live in anything like the same way as their and our remote ancestors. In any case, which hunter-gatherer societies should we choose? Humans have adapted to widely differing environments, from deserts to tropical forests to the frozen wastes of the Arctic, and the solutions they adopted to live in these places were equally diverse.
Zuk discusses a number of general evolutionary questions in her first few chapters, and then moves on to a more detailed examination of particular aspects of the 'paleofantasy', starting with diet. Although the benefits of adhering to a 'paleodiet' are widely touted, there is little agreement about what this diet should consist of, though meat figures largely. But is that what we are 'meant' to eat? What evidence we have suggests that our species has always been flexible in its diet.
In any case, the idea that our genes are fixed in the pre-agrarian era and cannot have adapted to any later diet is clearly wrong. A recurrent theme in this book is that evolution can, and does, occur over much shorter time spans than many people believe. One piece of evidence, discussed in some detail here, is the persistence beyond childhood of the enzyme, lactase, that enables adults to digest the lactose in milk. This development is quite recent and has appeared only in those people whose ancestors learnt to domesticate cattle and use them for milk.
There is no doubt that exercise is good for us and until quite recently practically everyone took much more exercise than is usual today. But what was the exercise pattern of our remote ancestors: long-distance running or short sprinting? There is evidence to support both views.. "It … is futile to look for the single best type of exercise, given our evolutionary heritage, though it's a safe bet that we would be healthier if we got up off the couch."
Still on the subject of exercise, Zuk has quite a detailed discussion of footwear and fashionable advice to run barefoot. She is doubtful about the soundness of this. A further reason for scepticism, which she does not mention, is recent evidence evidence that the Cro-Magnons wore shoes (see Lone Survivors). And enthusiasm among paleofantasists for barefoot running does not seem to be shared by modern hunter-gatherers; a recent TV programme showed a San hunter running down an eland, and the man was wearing shoes!
Zuk goes on to direct her sceptical gaze at claims for an evolutionary basis for our sexual behaviour, child-rearing practices, and notions of health. As she rightly points out, the idea that if we adhere to some fanciful version of how our early ancestors lived we will escape the supposed ills of modern living is a delusion. The mistake is to think that evolution has a goal, an ideal final state, which was reached by our ancestors and which we have now lost by living so 'unnaturally'. The truth is that those ancestors were not perfectly adapted to their conditions either—no species ever is. Evolutionary adaptation is always a compromise based on tinkering with our genetic inheritance.
In her final chapter Zuk looks to the future as she considers whether we are still evolving. She thinks we are, parting company here with those, such as Steve Jones, who think that modern culture has done away with natural selection. As she rightly says, human culture is as 'natural' as anything else in the world. Even if it could eliminate natural selection, changes in gene frequency would still occur thanks to genetic drift. But in fact Zuk has no difficulty in finding evidence for the continuing operation of natural selection today.
Zuk is an excellent exponent of popular scientific writing. Her tone is light-hearted and often humorous but she doesn't shirk difficult issues and all her statements are referenced in end notes.
See also Sense and Nonsense: Evolutionary Perspectives on Human Behaviour by Laland and Brown.
20 April 2013
%S What Evolution Really Tells Us About Sex, Diet, and How We Live
%A Zuk, Marlene
%I W.W. Norton and Company
%C New York
%G ISBN 9780393081374
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