“First they ignore you, then they ridicule you, then they fight you and then you win”. This is the famous Gandhi quote rephrasing a quote by a forgotten US union leader by the name of Nicholas Klien.
The roll of the Ridiculer is happily taken by Prof. Marlen Zuk whose new book “Palefantasy – What evolution really tell us about sex, diet, and how we live” has been published recently.
Zuk’s claim to fame seems to be the discovery that a certain kind of cricket went through a relatively rapid pace of evolution in one of the Hawaiian Islands. She is part of a small but brilliant group of evolutionary biologists that have found that evolution is not always as slow paced as had been once assumed.
What has turned Mrs. Zuk Anti-Paleo, apparently, seems to have been Prof. Lorain Cordain’s justification of the Paleo Diet, with the assertion that we haven’t changed genetically during the last 10,000 years. In the book she goes to the trouble of quoting, in vivid detail, a dramatic exchange she had with Cordain a few years ago:
“Why, I asked Cordain, has this inability to properly digest all of this common food persisted? Surely it should have been selected out of the population”. He was taken aback. The answer was obvious, he responded: “The sensitivity had been occurring only since the advent of agriculture, so humans haven’t had the opportunity to adapt yet”. I frowned. “Plenty of time”, I said. “But it’s only been ten thousand years” he said. “Plenty of time I repeated”. Now it was his turn to frown (end of quote).
A knockout victory no doubt, and it seems Cordain will have to buy the book if he wants to understand how come there was “Plenty of time”, or he might stay frowned forever.
Although the book deals with other supposedly maladaptations I will limit the discussion to nutrition.
Zuk discusses in detail two specific examples of post-agricultural genetic adaptations in foods. The first is the ability of North European and some Africans to produce lactase, the enzyme that allows us to consume milk past weaning. The second is the presence of multiple copies of salivary amylase producing genes in populations that tend to consume plenty of carbohydrates. Amylase helps to break starch into glucose, the cell’s source of energy.
Zuk later gives an additional example or two of adaptation to certain kind of post-agricultural foods in some groups. But all of them, believe it or not, managed to strengthen my conviction that Paleo is the smartest way to go.
Let me take the case of salivary amylase to demonstrate how Zuk’s examples may actually point to an opposite conclusion to the one she reached.
Here is the graph from the original Perry paper of 2007. The graph shows the distribution of the number of copies of the gene for salivary amylase among low and high starch consuming groups.
Whichever way you want to look at this graph, one conclusion is crystal clear – whatever constitutes full adaptation to a consumption of a high starch diet, many of us are not there yet. Just for argument’s sake let’s pick a number of copies in the middle, between chimps (2) and highly adapted starch eaters (15), say 8.5 copies ((15-2)/2+2) as a cutoff point representing reasonable adaptation. Of the high starch group only 15% are fully adapted and of the low-starch group only 9% are reasonably adapted. We don’t know what the total population number is, since we don’t have the ratio of the groups in the total population, but you should get the idea and it applies to the lactase adaptation as well – The adaptation is partial from two aspects: it is only partial in many of us and it is partial from a geographic point of view.
One of the common misconceptions about Paleo is that it strives to romantically imitate the original Paleolithic diet. The truth of the matter is that Paleo is nothing but a safety template.
Every decision must consider an alternative, so here are the alternatives that Zuk’s book presents:
- Eat plenty of starch and drink plenty of milk, to which some of us are fully, or more likely, partially adapted
- Eat plenty of meat and fat, to which we are all likely well adapted. (I didn’t see any argument from Zuk against adaptation to meat)
Another important point that Zuk fails to mention is that the main source of starch in western societies, wheat, has recently gone through some substantial genetic changes itself so even if some of us have adapted to consume wheat safely in the past, chances are quite slim that we have adapted to the consumption of the new Semi-Dwarf, gliadin laden strain in only 50 years. The same argument may apply to many other plant foods which are all presently going through a major genetic overhaul in the labs of Monsanto and the like. Homogenized and pasteurized milk is equally recent and unnatural and so are white sugar, fructose corn syrup and soya oils. In short the more rapid evolutionary pace that Zuk discovered is of little help in practice and even a superficial look at its details raise more reasons for concern than comfort.
I could stop here (and you can if you’ve had enough) but I just couldn’t leave two of several arguments I could comment on unaddressed:
- In chapter 5 Zuk says (or quotes Hamilton as saying, it is not clear): “What we are able to eat and thrive on depends on our more than 30 million years of history as primates and not on a single arbitrarily more recent moment in time.” How does that statement coincide with the claimed relevance of the rapid evolution theory is beyond me but even if it were true both Zuk and Hamilton fail to realize that as primates we received most of our calories from fat via fermentation by bacteria of the heavily fiber laden fruits that at least our closest primate relatives had consumed. The four times smaller colon that we have, compared to them is but one of many evolutionary changes that are unlikely to change as quickly as the one gene change that allows crickets in Hawaii to stay quiet in order to survive in the face of a new parasite. So if this statement is correct we should still be adapted to get about 50% of our energy from short chain fatty acids. (see my post on the Chimpanzee diet)
- Zuk, for some reason, feels that she must also prove that we ate plenty of plants during the Paleolithic. Here she is way off her area of expertise (and much closer to mine). I will not go into detail here and only say that the presentation of the subject is one sided and partial, to put it gently (here is a post on that subject). Zuk ignores two of the most cited ethnographic studies on the subject by Cordain and by Kaplan, both of whom arrive at very high hunting sourced foods (65% and 70-80% respectively), and brings instead a lightly cited paper by Marlowe with substantial methodological shortcomings that indicate the opposite. She employs the fact that bows appeared late on the scene to prove that only recently we have managed to obtain high quantities of animal food. The fact is that bows appear on the scene subsequent to the beginning of the mega-fauna extinction and the ethnographic record shows that they are mainly used to hunt smaller and faster animals. By the way, recent papers show that the mega-fauna extinction was largely man made, at least in Australia. So here is another methodological problem with extrapolating from the ethnographical record to the Paleolithic – Much larger animals were available then and man always preferred to hunt larger animals. Presumably then until recently it was easier for hunters to obtain meat so the ratio of hunted sourced meat would have been even greater than the ethnographic record shows.