Monday, March 11, 2013

The Fantasy of Paleofantasy

I've seen this book Paleofantasy positively reviewed several times now, John Hawks even wrote a tweet linking to an article praising this book (Shame on you, John). The latest gushing review is in Salon:
Four years ago, biology professor Marlene Zuk was attending a conference on evolution and diseases of modern environments. She sat in on a presentation by Loren Cordain, author of “The Paleo Diet” and a leading guru of the current craze for emulating the lifestyles of our Stone-Age ancestors. Cordain pronounced several foods (bread, rice, potatoes) to be the cause of a fatal condition in people carrying certain genes. Intrigued, Zuk stood up and asked Cordain why this genetic inability to digest so many common foods had persisted. “Surely it would have been selected out of the population,” she suggested.

Cordain, who has a Ph.D in exercise physiology, assured Zuk that human beings had not had time to adapt to foods that only became staples with the advent of agriculture. “It’s only been ten thousand years,” he explained. Zuk’s response: “Plenty of time.” He looked at her blankly, and she repeated: “Plenty of time.” Zuk goes on to write, “we never resolved our disagreement.”
Right off the bat, we can see the Salon reviewer is not a fan of paleo-type diets, nor even very familiar with them, because I'm pretty sure the leading "guru" of the "craze" would be Robb Wolf a former student of Cordain, perhaps tied with Mark Sisson's primal version of paleo.

I don't see any mainstream paleo type writer saying that there's been zero evolutionary changes in humans in the last 10,000 years.  Myself, I don't have a problem with the idea that natural selection has not only continued but accelerated, thanks to a larger population and perhaps increased selection pressure.

And every single review mentions the lactase persistance mutation as proof that human evolution happens quickly.
There are human examples, as well, such as “lactase persistence” (the ability in adults to digest the sugar in cow’s milk), a trait possessed by about 35 percent of the world’s population — and growing, since the gene determining it is dominant [ed. No it isn't, "lactase persistence behaves as a dominant trait because half levels of lactase activity are sufficient to show significant digestion of lactose" WIKI]. Geneticists estimate that this ability emerged anywhere from 2200 to 20,000 years ago, but since the habit of drinking cow’s milk presumably arose after cattle were domesticated around 7000 years ago, the more recent dates are the most likely.
In the case of lactase persistance, the mutation (actually two mutations, 13910 and 22018) is simply to have the body continue to produce lactase, something which all mammals do anyway, although they usually lose this ability, a condition known as hypolactasia, before adolescence. Mammals have been around for 160-200 million years and drinking milk is one of their defining characteristics, hence the name mammal. So it seems pretty likely that the adaption of continuing to be able to digest milk is a lot more simple than the adaptations necessary to adjust to a completely new substance such as gluten.

Or perhaps she is referring to the fact that lactase persistance has spread to 35% of the population in the last 7000 years? What about the 65% of the population that is lactose intolerant? If Ms Zuk thinks 10,000 years is "plenty of time" to adapt to staple foods then why hasn't the majority of the world's population adapted to milk? Obviously milk wasn't enough of a staple for much of the world's population to have been selected for lactase persistance, along with the fact that up until the modern age genes didn't travel across continents very quickly as groups were relatively isolated. Also, the fact that the lactose could be broken down by fermentation allowed access to it in the form of yoghurt and cheeses by lactose intolerant groups.

But if only 35% of the world's population has the ability to tolerate lactose, why would one think that the majority of people are perfectly adapted to "heart-healthy whole grains"? Much less to primal/paleo/ancestral bugaboos such as processed sugar, industrial seed oils, etc?

Just because the mutation for lactase persistance spread fairly quickly in some groups doesn't mean humans are perfectly adapted for eating grains, especially wheat.

A recent study in Nature found that dogs are better adapted to eating carbs than wolves. Which makes sense. Does that mean that dogs are perfectly adapted to carbs? Just because dogs show some adaption to carbs doesn't mean Rover is going to thrive on a diet of Wonder Bread.

There is a kernel of truth beneath all of this hyperbolic bullshit Ms Zuk and her sycophantic reviewers are slinging in order to sell her book. Something Dr Kurt Harris called paleo-reenactment, the idea that we are perfectly adapted to living in some imaginary stone age environment where starches were never eaten, no one ever got sick, and everything was sweetness and light. Not surprisingly, during her copious research for this book, Ms Zuk managed to Google up some of these people on message boards somewhere on the internet.

Zuk's talking points are all pretty thin gruel as far as I can tell, and I don't even have a PhD in biology, much less genetics. But I imagine her book will do pretty well from all the obsequious, non-critical reviews I've seen such as this.

Not that it really matters. No one is going to suddenly become tolerant of gluten because someone writes a book saying that, duh, we should all be adapted to that stuff by now. The truth will out, is already out there, and all of Ms Zuk's mendacious criticisms aren't going to change that, even if they do end up generating her a tidy little income.

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