Prof. Marlene Zuk (University of California Riverside), author of Riddled with Life: Friendly Worms, Ladybug Sex and the Parasites That Make Us Who We Are (Amazon, Google books), has a very nice short essay in The New York Times on the recent discussion of whether or not our dietary problems stem from our bodies being ‘out of step’ evolutionarily with things like Mars bars and Big Macs: The Evolutionary Search for Our Perfect Past. We’ve seen these sorts of arguments all over the place, that a ‘Paleolithic diet’ can make you healthy and banish bulges from inopportune places, after all, just look at Raquel Welch in 10,000 BC!
When I talk about diet and human evolution in my freshman class, I have to point out that there are a tremendous number of complications, including the fact that the vast majority of us do not have the cultural knowledge to get ANY nutritional resources out of the environment around us (see my earlier post with my slides from that lecture, if you like). It’s all well and good to say, ‘Eat meat, roots and berries,’ but that just means spending our time in the grocery store aisles a bit differently for most of us, not actually transforming the ways that we get food, how we relate to our environment, or even the quality of the meat, roots and berries we’re getting (after all, even the meat we get is from the animal world’s equivalent of couch potatoes, not the wild stuff on the hoof– or for that matter, dead on the ground where we can scavenge it).
Zuk draws on Leslie Aiello’s concept of ‘paleofantasies,’ stories about our past spun from thin evidence, to label the nostalgia some people seem to express for prehistoric conditions that they see as somehow healthier. In my research on sports and masculinity, I frequently see paleofantasies come up around fight sports, the idea that, before civilization hemmed us in and blunted our instincts, we would just punch each other if we got angry, and somehow this was healthier, freer and more natural (the problems with this view being so many that I refuse to even begin to enumerate them). It’s an odd inversion on the usual Myth of Progress, the idea that things always get better and better; instead, paleofantasies are a kind of long range projection of Grumpy Old Man Syndrome (‘Things were so much better in MY day…’), spinning fantasies of ‘life before’ everything we have built up around us.
Zuk describes how, she was initially enthusiastic about the ‘evolutionary mismatch’ argument around health and diet, but that, upon closer inspection: ‘The notion that there was a time of perfect adaptation, from which we’ve now deviated, is a caricature of the way evolution works.’ Zuk asks which particular stage in hominin evolutionary development was the age at which we were perfectly in harmony with our environment:
How much of the diet during our idyllic hunter-gatherer past was meat, and what kind of plants and animals were used, varied widely in time and space. Inuits had different diets from Australian aboriginals or Neotropical forest dwellers. And we know little about the details of early family structure and other aspects of behavior. So the argument that we are “meant” to eat a certain proportion of meat, say, is highly questionable. Which of our human ancestors are we using as models?
In fact, the idea that our bodies were perfectly suited to a particular environment is an adaptationist fantasy. Processes of evolution, including variation and natural selection, niche creation and co-evolution, even catastrophe and fluctuating rates of evolutionary change, suggest that adaptation is usually imperfect, with abundant glitches that, as long as they don’t constitute abject failures, usually continue to exist unless selection and variation conspire to find a way to get rid of them.
We have never been a seamless match with the environment. Instead, our adaptation is more like a broken zipper, with some teeth that align and others that gape apart. The paleontologist Neal Shubin points out that our inner fish constrains the human body’s performance and health, because adaptations that arose in one environment bedevil us in another. Hiccups, hernias and hemorrhoids are all caused by an imperfect transfer of anatomical technology from our fish ancestors.
I’ve been recently reading a book that I have to review which follows this line of thinking: that evolution shaped us for one sort of environment, but that civilization, technology, social life, and culture all demand something radically different from us, so we’re stuck. There’s an odd inconsistency there: on the one hand, we’re perfectly adapted to paleolithic life; on the other hand, our bodies just can’t get with the last 10,000 or 50,000 years of change. Usually the argument is that ‘we’re just changing too fast now to adapt.’
I think the biological evidence points to the fact that both of these impressions is incorrect, as Zuk suggests: we are neither so perfectly well adapted to foraging (or scavenging or living in trees or whichever stage we develop paleonostalgia for) nor are we so ill-suited for our own environment (in spite of our health problems, we actually live a long time compared to our ancestors, for example).
So before we start waxing nostalgic about all the health benefits of a Pleistocene diet, perhaps we should remember that our ancestors’ food often came in this nasty packaging which tended to run away, attack them, or just go missing entirely when they were really hungry. Zuk’s conclusion is a very balanced one:
This isn’t to say that we wouldn’t be better off eating fewer processed foods. And certainly we have health concerns that never struck our ancestors. But we shouldn’t flagellate ourselves for having modern bodies, and we shouldn’t assume that tweaking our diets or our posture will rescue us from all our current ills. That’s just a paleofantasy about the future.
We are, quite simply, a species of our Age, shaped by the environmental forces around us, just as our ancestors (and us) were also shaped by their Age (whether the Holocene, Pleistocene, or earlier). We drag the history around in our bodies, but we also bear the stamp of our own time, especially in things like diet, as the food choices we make end up affecting the very molecular structure of our bodies and brains. I don’t think we’re fat or have heart disease or live longer because we’re stuck in Stone Age bodies, but rather because we’re fashioning Information Age regimes of food, activity, and environments. We tend to look at our bodies and see their inadequacies, but we could just as easily see them as the perfectly logical products of the developmental processes we create, for all their strengths and weaknesses.
Update: If you still haven’t had enough of discussions about diet and evolution, I’ve put up a brief discussion of Richard Wrangham’s work over at the new site: Food for thought: Cooking in human evolution. And bonus, Prof. Wrangham actually responded to the post and dressed me down for presenting a simplified version of his argument.