Sunday, October 5, 2014

Learn about evolution and laugh

Most readers of newspapers or magazines are likely to have encountered evolutionary explanations and worse, justifications for almost any human activity, from rape to raw meat diets. There are several things wrong with these melodramatic logical leaps. In Paleofantasy, Marlene Zuk masterfully, and with characteristic bluntness, debunks every fallacy and fantasy, walks you through the basics of evolutionary theory and makes you laugh out loud, all at the same time.

The subject matter for this book is brilliant, because as humans, which one of us isn’t really quite fascinated by our own history, and what it might mean for our present and future behaviour? There are a slew of well-written introductions to evolution on the market, many of which spend a great deal of effort trying to convince readers that evolution does indeed occur. There is nothing wrong with these books, but they tend to attract readers who are already members of the evolutionary choir, rather than people who might otherwise consider themselves largely uninterested in science. Almost anyone would be interested in questions like: Are humans still evolving? What does evolution tell us about what we like to eat, do for fun or why we get old and die when we do? In answering these questions, Zuk brilliantly explains both the key theory and some fairly abstruse methodology with such clarity and humour that without realising it, the reader is given a first class grounding in modern evolutionary biology. That is what makes this book the perfect gift and ideal reading in an introductory course for non-biology majors while still being great fun for any biologist, who must often trot out similar vignettes for friends and family.

One of the most commonly encountered confusions are arguments along the lines of “our ancestors evolved to do X (where X can be running barefoot, or being promiscuous) therefore we are justified in doing X. Paleofantasy steps through aspects of human life, from diet, to exercise, sex, birth, death and disease, and two threads run through the book: firstly, that what is “natural” or “evolved” does not equal what is good, and secondly, that it’s usually jolly tricky to know what is “natural” in our evolutionary past.

Advocates of paleolifestyles seldom agree on what is natural, and for good reason. There simply isn’t much evidence for a single, static and decipherable Flintston-esque evolutionary past for humans, so it’s anyone’s guess what our ancestors did, which allows for personal preferences to run amok. Zuk is particularly good and finding stunningly funny quotes from earnest Paleo-bloggers who rhapsodize over the beneficial effects of subsisting on pork belly or doing spontaneous busts of press-ups and sprints to simulate the heaving of boulders and the need to flee from enraged rhinos in our so-called evolutionary past.

Zuk’s main point, which she dedicates a chapter to, is that evolution can happen a lot faster than you might think, and that it can occur at very different speeds. So even if there were a relatively long period of environmental stability in our past, that doesn’t mean we haven’t changed genetically since the invention of agriculture. Besides, humans pride themselves on their flexibility and ingenuity, so it should come as no surprise that in our evolutionary past, we were probably rather good at moving about, living in a wide range of places and with a wide range of social systems. We are generalists like rats, and we like to think we’re smarter. This chapter on rapid evolution is probably my favourite, because it introduces some of the most classic examples of rapid evolution like finch beaks and viruses, but also displays some of Zuk’s own work on Hawaiian cricket males who have evolved in the space of a few years to stop serenading females because the song also attracts deadly parasites that would otherwise kill the males before they had a chance to mate.

In the very next chapter, Zuk discusses the poster child of human evolution – the ability of cattle-herding populations to digest milk as adults. Not only is this example a jolly good bit of evidence for rapid, culturally imposed (you could say self-inflicted) human evolution, it also gives Zuk the chance to explain some tricky methodology with admirable clarity and simplicity. And it will give readers a good idea of just how biologists work, from collecting the blood and spit of people around the world to the logic underlying computer tests.

Peppered throughout the book are not just pictures of how science is done, but also an affectionate but perceptive portrayal of scientists as people. Starting with her own delightfully distinctive, no-nonsense style, wry humour and sensible brand of feminism, Zuk is superb and showing how every scientist has his or her own (often enchanting) biases and mannerisms. She lets slip that Linnaeus, father of modern biological classification, decided to name the main plant groups according to the numbers of husbands or wives each plant had. Similarly, the Grants, who measured natural selection in action on Darwin’s finches in the Galapagos come alive in her anecdote about their group meeting on returning from the field after a massive El Nino changed the landscape dramatically from brown and barren to a verdant paradise. The Grants and their students could barely contain themselves at the sight of photos, excitedly remarking upon every tree, resplendent in unaccustomed greenery. In contrast, Zuk, then a student from a different lab, found this so tedious she had to slip out. That anecdote and many others, captures both the thrilling and the mundane in science, practised by subjective scientists. For a superb book on the Grants' work, I highly recommend The Beak of the Finch.

Paleofantasy doesn’t simply showcase instances of evolution by natural selection as demonstrated by Darwin’s finches. Zuk deals directly with the fact that evolution is simply defined as change, and so can occur in different ways, of which selection, whether natural or human is merely one. For those who might want reassurance that this is indeed a good introduction of evolutionary theory, Zuk explains concepts like drift, the role of contingency and history in evolution, adaptive landscapes, arms races and the ideas that evolution is a tinkerer. If these phrases are Greek to you, read the book. She also puts to rest the notion that evolution is in anyway directed, or that any living thing today could be “more evolved” or superior to any other living thing, since they have all been evolving for equally long. 

The only aspect of evolution I would have liked to see more of in this marvellous book is conflict. Perhaps this is because Zuk didn’t wish to put off people with a rosier view of human nature, but as we’ve established, nothing in evolution prescribes or justifies our moral choices. She does present the intriguing notion that humans have an unusually extended childhood as a way for parents to have a lot of relatively cheap labour. However her chapter on family remains relatively silent on the converse scenario in parent-offspring conflict, where children can be thought of as little machines for manipulating parents into caring more for them than for their current or potential siblings.

There is a delightful extension of the theory behind parent-offspring conflict, proposed by David Haig, which essentially explains much of behaviour or even foetal growth in terms of conflict between genes inherited from mums and dads within an individual’s body. It’s as if your parents could extend their evolutionary battle to your body, rather than just tussling over who is left holding the baby. For instance, Haig just proposed that genes inherited from fathers are the copies that make babies cry more at night, the better to exhaust mum so she takes longer to produce a competition in the form of a sibling. In contrast, copies of the same genes inherited from mum would make babies less likely to cry. This, and all other instances of Haig’s conflict explanation for “genomic imprinting” – the phenomenon where a gene’s actions differ depending on the sex of the parent they came from, rather than the actual gene sequence – is contingent on males being unable to guarantee that they will always be the exclusive mate of a female. As a result, genes from fathers will benefit if they can cause offspring to behave in relatively selfish ways, such as growing rapidly in utero, while genes inherited from mothers can best counter this by having the opposite effect on offspring, such as silencing signals to grow. It’s not that mothers don’t need healthy offspring, but they would pass on the most genes if they could divide up their lifetime’s resources evenly across an optimal number of children. In contrast, males who might only father one or some of that mother’s children, will have not genetic interests in her other progeny, and their genes would do best if they could cause their offspring to exploit mum as much as possible, to the detriment of mum’s other offspring. My favourite popular books on the general subject of conflict (and cooperation) are still The Selfish Gene and TheExtended Phenotype by Richard Dawkins. Please don’t get put-off by his later polemical pieces like The God Delusion.

Zuk herself is arguably most famous for the “Hamilton-Zuk hypothesis”, which is founded on the continual conflict between sexually producing organisms and their parasites. The notion is that the main way for relatively slowly reproducing things like humans to stay one step ahead of bacteria and viruses is to keep coming up with new combinations of immune defences encoded in our genes. These genes can be reshuffled, where genes from our mum and dad are literally recombined every time one of us makes eggs or sperm, and then they get paired with a new mixture when we have sex. The sexiest mates should be the ones that will help make children with the most varied combinations of genes, the better to confound those rapidly reproducing parasites. If you want a more thorough treatment, you should read Zuk’s book Sexual Selections. But if you just want a good general Christmas present for anyone who likes reading, please consider Paleofantasy.

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