A few weeks ago I read Paleofantasy: What Evolution Really Tells us About Sex, Diet, and How We Live, by Marlene Zuk, a professor of ecology, evolution and behavior at the University of Minnesota, USA. I was drawn to the book after reading a review about it in Science, and I was not disappointed. The book makes for an entertaining and easy read, taking us through what is known about human evolution and how scientists investigate the matter, while debunking some common popular ideas about our evolutionary history and how we should “behave” according to it.
What is a paleofantasy? Basically, it’s the idea that anatomically modern humans spent tens of thousands of years living in an environment very different from the one we know today, to which they were well adapted, and that so much change occurred in the past 10,000 years that our bodies have not had time to adapt, resulting in a mismatch between our genes and our environment. Paleo lifestyle proponents therefore argue that by adopting a lifestyle more like that of our hunter-gatherer ancestors, we would be healthier.
When it comes to living a paleo lifestyle, you can find a whole range of ideas, like not eating any starch or running barefoot, and some people take the issue very seriously, perhaps to the extreme. At the beginning of her chapter “Cavemen in Condos”, Marlene Zuk describes some of these paleo lifestyle followers: subsisting mainly on meat (cooked or not is a matter of debate), exercising in intense bursts of activity (imagine running as if escaping a predator), and frequently donating blood (you did not escape the predator completely unscathed). Altogether, men looking “like the cast of Pleistocene Twilight” according to John Hawks, an associate professor of anthropology at the University of Wisconsin-Madison, USA.
In her book, Marlene Zuk tackles common paleofantasies about diet, love, exercise and child-rearing. But more importantly, she uses this as a starting point to discuss in an engaging and accessible way the hard science on human evolution (or even evolution in general). She explains basics concepts such as genetic drift, gene flow or natural selection, describes how we can learn anything about our ancestors from thousand year-old DNA, bones or teeth, gives us a short recap of the history of our genus, Homo. Importantly, she also presents examples of how certain human traits appeared fairly recently, contrary to a common popular belief that evolution always takes hundreds of thousands of years or more to happen. The persistence of lactase (the enzyme responsible for the digestion of lactose, a type of sugar found in milk) beyond the age of weaning in humans is one of them: researchers are still trying to trace its appearance more precisely, but so far some calculations suggest that the form of the lactase gene allowing milk consumption in adulthood may be anywhere between 2,200 and 20,000 years old; others put the pin at around 7,000 years old.
Marlene Zuk also reminds us that we (or any organism for that matter) did not evolve to be or evolve to do this or that. Evolution has no specific end goal. Neither has any organism ever been a perfect match with its environment and stopped evolving from there. As she puts it, “[N]o organism gets to a point of perfect adaptation, heaves a sigh of genetic relief, and stops”. Most traits are “good enough” solutions rather than perfect adaptations to a given environment. So looking back at our cavemen ancestors and thinking “yep, that was it, that’s how we humans are supposed to live” not only ignores the fact that humans have kept evolving, but also idealizes a past that was actually far from perfect.
Paleofantasy is not a book that’s going to tell you how to eat and live. However it is a book that will probably teach you a few things about evolutionary biology, anthropology and genetics, while keeping you entertained with examples and anecdotes. And let’s not forget the recurring theme of the book, debunking paleofantasies: if you ever meet a New-Yorker convinced that running barefoot and eating meat three times a day is the only way to go (together with living in a high-rise and wearing shiny Italian leather shoes to work), you will be prepared.
Paleofantasy: What Evolution Really Tells us About Sex, Diet, and How We Live. Marlene Zuk. W.W. Norton: 2013.