Critics sometimes use the example of lactose tolerance as a change that occurred rapidly and that changed radically what humans can consume. Cordain:
Because humans normally maintain lactase activity in their guts until weaning (approximately 4 years of age in modern-day hunter-gatherers), the type of genetic change (neoteny) required for adult lactase maintenance can occur quite rapidly if there is sufficient selective pressure. Maintenance of childlike genetic characteristics (neoteny) is what occurred with the geologically rapid domestication of the dog during the late Pleistocene and Mesolithic [Budiansky 1992].Whether humans can or did evolve in an adaptation to agriculture, specifically the eating of grains, there's a relatively easy comparison to make, whether different ethnic groups have differing nutritional requirements or physiology. Some groups have been exposed to agriculture for hundreds of generations, other for very few:
The complete re-arrangement of gut morphology or evolution of new enzyme systems capable of handling novel food types is quite unlikely to have occurred in humans in the short time period since the advent of agriculture. Some populations have had 500 generations to adapt to the new staple foods of agriculture (cereals, legumes, and dairy) whereas others have had only 1-3 (i.e., Inuit, Amerindians, etc). Because anatomical and physiological studies among and between various racial groups indicate few differences in the basic structure and function of the gut, it is reasonable to assume that there has been insufficient evolutionary experience (500 generations) since the advent of agriculture to create large genetic differences among human populations in their ability to digest and assimilate various foods.Cordain, like myself, also doesn't think too highly of the "blood type diet", it being far too simplistic to make much sense.
It's really a weird hypothesis to think that just because humans got smarts, blue eyes and the ability to tolerate lactase or resist malaria, they could/should also have adapted to carbohydrate-rich agricultural products.
ReplyDeleteEspecially when it's refined carbs, like sugar, that do most damage to our body. Such carbs have been in the Western diet for, what 100-200 years? That's 3-7 generations -- tops.
If humans would have lived under conditions where nothing but carbs (over 90% of in-take) where available for over 500 generations continuously, I'd believe selection pressures could be strong enough. But that's not the case. At all.
Think about it: What if only the plant-eaters would have survived in the West? I don't think we'd last for long.
There has been very few studies about the racial differences in food requirements. Chinese have definitely longer guts than Europeans, possibly to digest rice. Inuits are not long existing race, they moved to the north a few generations ago. Fermented food is not unknown in the West, if we eat less of it than the Koreans is because we are different.
ReplyDeleteEthnicity matters. Europeans and Asians tend to do better on the Western diet than people who haven't had as long to adapt to agriculture. On the same diet, Europeans tend to have a lower incidence of heart disease, obesity, and diabetes.
ReplyDeleteIf you are a Pima Indian, for example, the modern Western diet is simply poison.
Some people can stand a lot more carbohydrate in their diet than others. And I'm sure it's very heritable.
Whatever your genetics, sugar is probably a stupid idea for anyone.
It's a mistake to think of this in binary terms (people either adapted to an agricultural diet or not). Obviously some populations are going to have some adaptations that allow them to benefit more (or be harmed less) by grains, or whatever other non-ancestral food they need to be able to eat. You can find mutations in Asian populations that favor starch metabolism. The extreme paleness of Baltic European populations may be an adaptation to a grain-heavy diet. And I would be very surprised if there weren't analogous adaptations to maize, potatoes, and manioc, in areas where those plants provide(d) a lot of calories to the population.
ReplyDeleteBut if you turn the question around and ask whether this process of adaptation is complete, the answer does seem to be a resounding 'no'.
Apparently the Pima Indians do not only eat lots of carbohydrate, but much of their food is government-supplied, white floury, processed and canned garbage. Add to that the fact they share alcoholism and other social pathologies with the other tribes, and the case that they're merely reacting to a high carb diet because they haven't had enough time to adapt to it becomes much weaker. Their brothers on the other side of the border, the Mexican Pimas, apparently do quite well on a diet of beans, squash, and corn, minimally processed.
ReplyDeleteDespite the Mexican Pima's stellar health profile compared to the American Pima, they still manage to get a lot more diabetes than the regular Mexican population. And this is with high physical activity levels.
ReplyDeleteComplex carbohydrates are far better than refined carbohydrates, but they're still not great for you.
In the surveys of the genome for signals of recent selective sweeps, two categories of genes that are enriched for such signals are fat metabolism and protein metabolism, IIRC.
ReplyDeleteJust playing around with the HGDP browser (google it), I've found 3 genes that almost surely reflect recent... not adaptations, but attempts to cope with an agricultural diet. There are surely others too.
We're probably not hitting on fundamentally new solutions like a four-chambered stomach, but just finding that one guy whose genes make him only get mild diabetes compared to debilitating diabetes when he eats potatoes or corn all day.
Cordain's right that the first-order picture is that we haven't changed much fundamentally, but the genetic evidence of recent selection makes us expect population differences in how badly hit a group will be -- e.g., Africans being hit harder than Europeans. Which is what we see.
We clearly need much more research in the field of 'ethnomedicine,' that is tailoring health treatment(s), diets, exercise, etc to a a person's specific ethnic background.
ReplyDeleteIn fact, I think that in the future ethnomedicine will become the norm and the 'one size fits all' model of modern medicine will be abandoned.
If carbohydrates are bad, why do I feel fatigued on a low carb diet, and have the subjective sensation that my IQ has dropped 10 to 20 points. I also have the impression that I need 1 or 2 hours more sleep while on the Atkins diet.
ReplyDeleteThe Viking
Viking --
ReplyDeleteIt feels like the flu when you start a low-carb diet. Wait until a few weeks after you start. You'll be just as sharp as ever, I promise. The sugar cravings even go away.
- "Evolution faster when it's warmer" - http://news.bbc.co.uk/2/hi/science/nature/8115464.stm
ReplyDeleteCould explain why there us so much more genetic diversity amongst equatorial Africans as opposed to the White Europeans and Asians who live in colder northern climates.
"Could explain why there us so much more genetic diversity amongst equatorial Africans as opposed to the White Europeans and Asians who live in colder northern climates."
ReplyDeleteIt could, but the usual explanation is that more genetic diversity exists where people have lived the longest. They've had more time to diversify. That's one of the principle supports of the "Out of Africa" hypothesis: humans have been in Africa longer than anywhere else because we find more genetic diversity there.
My question is if I am supposed to eat truly paleo and MY paleo ancestors were Mexican Indians, why shouldn't I eat corn, sweet potatoes,beans,peanuts, and chocolate in moderation?
ReplyDeleteI have been thinking about it for quite a while. There probably is some adaptation, though most likely suboptimal. And it would most certainly help to know the ancestors ate on an individual basis. Ethnicity is complicated as migrations happened a lot. Most British people are actually descendants of Basque hunters-gatherers and have little to do with the Celts - the earlier farmers. Apparently some Ashkenazi Jews are genetically related to Turks (Khazars).
ReplyDeleteThen, there is class, with peasants eating more carbs (but also gree veg) throughout ages and gentry eating more game, but probably also more honey and later sugar.
Even diet of a mother during pregnancy affects genes expression in children. And so does stress.
There is no one diet, though paleolithic diet is probably the best for most. But not for all.
Pure speculation: You can tell who is genetically better adapted to neolithic and modern dietary practices, because they're the people who can eat a diet with lots of bread and other modern starchy foods whilst remaining lean and relatively atheletic. We all know they exist, and they seem to be found in every ethnic group.
ReplyDeleteThe rest of us (i.e. people who get fat easily, or remain skinny and weak, on a modern diet) are the people who aren't so well adapted.