Evolution didn't just stop with the invention of agriculture. Genetics have changed and there have been some genetic changes in response to agrarian foods. These genetic changes generally only affect a certain percentage of the population, often from a particular region. While paleolithic foods seem to be the best for ALL people, knowledge of these genetic changes can be useful for making food decisions like whether or not to eat dairy or how much salt to include.
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on September 27, 2010
at 07:59 PM
I've been looking back through a lot of Stephan's older posts, and there's some really great stuff. Not that we didn't know that already. But I came across a nice post, short and sweet, "Grains and Human Evolution", which makes two important points (and in July of 2008, which is practically prehistory in the paleo world): i. Even if there is evidence of grain agriculture 10,000 or 11,000 years ago, it was not widespread until much later -- in the case of many African or New World groups, under a 1,000 years or even 0 years, practically speaking. ii. Nevertheless, there is evidence of some adaptation to grain consumption. And Stephan actually points to particular genes as candidates. Have a look.
He leaves us with the overall conclusion that there has been some adaptation to grains, but, put briefly, not enough.
I'd like to suggest -- and I know this is dangerous territory -- that whenever we are engaging in evolutionary speculation, we consider in each case what exactly the pressure would be that resulted in the genetic change. Because keep in mind that for one adaptation to survive such that all the members of a population have it, everyone else who didn't have it had to die. I understand that this is often a matter of degree. But not always -- there's a reason why essentially all Africans have dark skin and essentially all Europeans do not. If you had dark skin in Europe you eventually would not have been able to produce enough Vitamin D from the sun, and you would die without leaving offspring. The disadvantages for you were great enough to prevent you from reproducing -- either from failure to survive until the age of reproduction, or failure to attract a mate because of your relative sickliness, or failure of you and your group to survive in warfare against a healthier group. I'm sure there are others out there who are much more familiar than I with the various pressures on genes. If I'm missing something please correct me.
The main point is not to fall into the assumption that just because your ancestors come from a certain place that means they "soaked up" the food of that place. We of all people should be wary of this kind of reasoning, because we know that the persistent eating of certain things may be perfectly OK for the genes, even if not OK at all for the individuals who are the vessels for those genes. The perfect example, of course, is grains.
on September 27, 2010
at 07:20 PM
You mentioned dairy, which one has to be lactose tolerant to eat. Lactose tolerance, or the ability to make lactase in adulthood, apparently evolved independently in both Northern Europe and Northern Africa. It is, in fact, a genetic adaptation to a new food source. I'm a product of Northern European genetics and I happen to know that I'm lactose tolerant, because I don't get a case of the bloated, gassy trots when I eat dairy. But I don't eat dairy because I'm afraid it might cause chronic low-level inflammation or other systemic problems like gluten and lectins do.
And like milk, I can eat grain-derived foods with no immediate problems whatsoever. The whole problem with these neolithic foods is that they don't just kill you today like poison would, but cause problems that only manifest over extended periods of time. And this makes the effect hard to correlate with the cause. Even today, some people, even doctors, just can't seem to relate type-2 diabetes to a lifetime of high carbohydrate consumption.
So even if I'm genetically adapted to eating dairy, the fact that it doesn't make me immediately overtly sick does not mean that it is not causing me harm. But maybe it's not. How would an individual like me know one way or the other, except to wait a few decades and see?
In my case, I've just decided to adopt the paleo diet and skip grains and dairy, despite the lack of any obvious problems. But I'll tell you one thing: I miss the hell out of a toasted sesame bagel with cream cheese, smoked salmon, and capers.
on September 28, 2010
at 04:00 AM
I read somewhere that about 20% of the human population can produce some level of phytase in the gut. Phytase breaks down phytic acid and makes it safer and more digestable. The only advantage to producing phytic acid would be to help with the digestion of phytic acid rich foods like nuts and grains. However, it just occured to me that this adaptation may have originally been to help with digestion of nuts or some other nongrain food item. Grains may have had nothing to do with it originally!
Also interesting, the news recently carried some blurbs about how Japanese often have a bacteria in their gut that allows them to better digest seaweed like nori. This is not necesarily a human evolution, but interesting nonetheless. Bacteria evolve faster than humans and their evolution then effects us directly. Since their survival and our survival are intimately linked, it makes for an interesting situation.
on September 28, 2010
at 12:27 PM
I'll make this a wiki so that YOU and I can keep adding to it:
- Starch digestion: "We found that copy number of the salivary amylase gene (AMY1) is correlated positively with salivary amylase protein level and that individuals from populations with high-starch diets have, on average, more AMY1 copies than those with traditionally low-starch diets."
- Folate metabolism, though it's possibly epigenetic. Either way, some people seem to need more folate than others.