Tuesday, June 24, 2008

what our ancestors ate

I found a remarkable website called BeyondVeg.com, which is absolutely chock-full of information about nutrition, mostly from a human-history standpoint. The author is a former vegetarian and raw-food enthusiast who found his health deteriorating after many years of eshewing animal products. He's very frank about his change of paradigm, and refreshingly free of finger-pointing.

There are pages and pages and pages of discussion here, far too much for me to read--much less (ahem) digest--at a sitting, but I'm deeply intrigued by "Setting the scientific record straight on humanity's evolutionary prehistoric diet and ape diets" and even more so by the updates to that essay. Some samples:

  • "...recent findings pointing to a correlation between increasing levels of animal flesh in the diet over the eons at the same time the human brain was in the process of near-tripling in size..."

  • "Lack of sufficient intake of long-chain fatty acids in the diet would be a limiting factor on brain growth, and these are much richer in animal foods than plant. (Relative brain size development in herbivorous mammals was apparently limited by the amount of these fatty acids in plant food that was available to them.) Given the foods available in humanity's habitat during evolution, the necessary level of long-chain fatty acids to support the increasing size of the human brain would therefore presumably only have been available through increased intake of flesh."

  • "human cranial capacity has decreased by 11% in the last 35,000 years, the bulk of it (8%) in the last 10,000. ...this correlates well with decreasing amounts of animal food in the human diet during this timeframe.(...[also] correlates with the dawn of agriculture 10,000 years ago.)"

  • "the brain (20-25% of the human metabolic budget) and the intestinal system are both so metabolically energy-expensive that in mammals generally (and this holds particularly in primates), an increase in the size of one comes at the expense of the size of the other in order not to exceed the organism's limited "energy budget" that is dictated by its basal metabolic rate. The suggestion here is not that the shrinkage in gut size caused the increase in brain size, but rather that it was a necessary accompaniment. In other words, gut size is a constraining factor on potential brain size, and vice versa."

All of this is fascinating to me--it addresses some questions I had, in a non-hysterical and well-researched voice that is informative and easy to read. Even better, he talks about the spread of agriculture and cooking worldwide, and discusses the correlation between genetic origins--what part of the world your ancestors came from--and ability to thrive on certain foods, particularly milk and grains.

"Another interesting example of the spread of genetic adaptations since the Neolithic has been two specific genes whose prevalence has been found to correlate with the amount of time populations in different geographical regions have been eating the grain-based high-carbohydrate diets common since the transition from hunting and gathering to Neolithic agriculture began 10,000 years ago. (These two genes are the gene for angiotensin-converting enzyme--or ACE--and the one for apolipoprotein B, which, if the proper forms are not present, may increase one's chances of getting cardiovascular disease.)[123]

In the Middle East and Europe, rates of these two genes are highest in populations (such as Greece, Italy, and France) closer to the Middle Eastern "fertile crescent" where agriculture in this part of the globe started, and lowest in areas furthest away, where the migrations of early Neolithic farmers with their grain-based diets took longest to reach (i.e., Northern Ireland, Scotland, Finland, Siberia). Closely correlating with both the occurrence of these genes and the historical rate of grain consumption are corresponding rates of deaths due to coronary heart disease. Those in Mediterranean countries who have been eating high-carbohydrate grain-based diets the longest (for example since approximately 6,000 B.C. in France and Italy) have the lowest rates of heart disease, while those in areas where dietary changes due to agriculture were last to take hold, such as Finland (perhaps only since 2,000 B.C.), have the highest rates of death due to heart attack. Statistics on breast cancer rates in Europe also are higher for countries who have been practicing agriculture the least amount of time"

I'd never seen this correllation spelled out so simply. I'd suspected it, myself, when someone asked me why the Chinese ate so much rice but didn't get fat*; the only thing I could suggest was that the Asian genetic pool had adapted to heavy rice consumption. Nobody was willing to buy that, though, since we've all been conditioned to think that evolutionary changes take millions of years to enact.

Well, maybe on the bone-structure level. But how can a paleontologist know what the gut flora of Australopithecus looked like? And how many generations of bacteria can live and grow and die in the span of one human's gut's life?

"The difference in time since the advent of Neolithic agriculture between countries with the highest and lowest incidences of these two genes is something on the order of 3,000-5,000 years,[126] showing again that genetic changes due to cultural selection pressures for diet can force more rapid changes than might occur otherwise.

[however]"...Nobody yet ... really knows whether the observed genetic changes relating to the spread of milk-drinking and grain-consumption are enough to confer a reasonable level of adaptation to these foods among populations who have the genetic changes, and the picture seems mixed."

Nevertheless, it's a fascinating concept, and those of you who are interested in this kind of thing will probably enjoy further reading.

*By the way, it's not entirely true that the Chinese don't get fat. The women tend to get quite plump when they move to America, and there's a famous kung fu fighter who was very slim and trim until he went to work for the Emperor and had access to the banquet table--he died a young man, and very obese.

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