More on evolutionary approaches to diet

New York City mayor, Michael Bloomberg, has gotten a lot of attention with his recent announcement to institute a partial ban on large-size soda options in the city. The initiative, meant in some ways to address the growing problems of obesity and metabolic-related disorders (e.g. diabetes), follows very much the line of thought put forward in the 2008 book, Nudge, by Richard Thaler and Cass Sunnstein. That book argues that large-scale policy initiatives are politically difficult to pass but that there are a lot of subtle, seemingly small-scale regulations, designed to help people make better choices, that would be easier to pass and equally as effective. Coming out of the field of behavioral economics (which itself borrows heavily from evolutionary psych, human behavioral ecology and other evolutionary fields), the basic argument is that the government can and should serve a role in helping citizens make better choices. The classic example from the book is requiring grocery stores to stock healthier food options in the front of display cases (studies show grocery store clients default to the placement of items a surprising percentage of the time), so that, without any active manipulation, people will eat healthier.

The book has been criticized for promoting an overly paternalistic (or merely parental) form of governance, but it is clearly the intellectual source of Bloomberg’s plan. Dan Lieberman, professor in the Department of Human Evolutionary Biology at Harvard University, has an op-ed piece in the NY Times supporting the plan:

Simply put, humans evolved to crave sugar, store it and then use it. For millions of years, our cravings and digestive systems were exquisitely balanced because sugar was rare. Apart from honey, most of the foods our hunter-gatherer ancestors ate were no sweeter than a carrot. The invention of farming made starchy foods more abundant, but it wasn’t until very recently that technology made pure sugar bountiful.

The food industry has made a fortune because we retain Stone Age bodies that crave sugar but live in a Space Age world in which sugar is cheap and plentiful. Sip by sip and nibble by nibble, more of us gain weight because we can’t control normal, deeply rooted urges for a valuable, tasty and once limited resource.

John Hawks, professor of Anthropology at the University of Wisconsin, responds:

“We have evolved to need coercion?!”

Evolution has a role in the science of obesity. It’s undeniable that our evolved preferences can be maladaptive in today’s industrialized food environment.

But coercion? Guess what? We already have coercion. There’s extreme social coercion against the obese in this country.

Both are correct. We certainly have evolved to enjoy the taste of, and even crave, sugar, salt and fat. None of these things were easy to come by during our Paleolithic past, but are now available in super-abundance, a dynamic that sets us up for a lot of metabolic and dietary health problems. But it is also true that obesity is highly stigmatized in this country and not solely the result of an individual’s dietary or lifestyle choice. Obesity has genetic, epigenetic and developmental aspects that place constraints on the role of behavior.

John goes on to note:

Notice: It’s the state that’s coercing children to be in school all day, where they are denied access to healthy food and physical activity! In this coercive environment, the federal government provides two free unhealthy meals a day for poor children. Seriously: If you want to bring an evolutionary perspective to bear on this question, look at the effects of eight hours of daily sedentism with an average 1200 kcal/day on a free school breakfast and lunch –not even counting after-school snacks and supper. The state is using its enormous coercive power to force children to become fat.

The choice between which correct argument to value more highly comes down to a personal choice about the role of government, but what strikes me is how much the argument parallels the writings of a former Harvard professor and Wisconsin graduate student (in classics), Earnest Hooton (1887-1954). In his 1939 book, Twilight of Man, Hooton writes (pp 294-295):

Now, when we add together all of man’s original or inherited sins, we arrive at a sum total of potentialities for an evolutionary mess which seems a trifle depressing, even to an incorrigible optimist like myself. Evidently the optimum functioning of all of the indifferently constructed parts of the organism is essential for a tolerable state of well-being.

First of all, we have that delicately adjusted, upright spine with its dangerous lumbar curve. Even before the infantile vertebrae are completely transformed from cartilage to bone, we begin to prop up the babies in a sitting posture which is likely to distort that plastic spine. Soon we thrust them into schools where they sit for hours acquiring rudimentary scholarship and advanced scoliosis, or lateral curvature of the spine. Meanwhile the shoulders are hunched, the chest contracted, and the organs of vision strained by premature concentration upon the dubious wisdom of the printed word.

At a deeper level this argument brings up the challenge of the extent to which evolutionary thinking can and should be incorporated into daily living. Evolution certainly can provide valuable knowledge that informs broad aspects of our daily lives, but it can also move quickly into slippery areas of saying what we, as the current evolutionary iteration of “humans,” are meant to be. It is important to remember that even from a strictly evolutionary view, there is no such thing as perfection (much as there are not “ideal” or “pure” types of things). It is theoretically impossible for the members of a population to simultaneously occupy an idealized adaptive peak (i.e. Haldane’s mutational load), which is a good thing, as the homogeneity of such a position would render further evolution impossible.

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About Adam Van Arsdale

I am biological anthropologist with a specialization in paleoanthropology. My research focuses on the pattern of evolutionary change in humans over the past two million years, with an emphasis on the early evolution and dispersal of our genus, Homo. My work spans a number of areas including comparative anatomy, genetics and demography.
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