Gregory Cochran and Razib Khan: The Speed of Human Evolution

[Al B. Sure!]

I can't sit here and listen for an hour but I tried to go to the times on some of the points, but the times don't seem to be right. They're not talking about helmets at 06:23.

[Al B. Sure!]

The talking about helmets is at ~24 minutes. They don't say much about it, though. How much selection pressure can the wearing of helmets have on the thickness of skulls? Seems a little odd. Do American Indians who never developed helmets, as far I know, have thicker skulls? They say nothing of that.

[Felch]

The times that are listed are durations. So there are introductions then 11:28 is about the book, then the next 4:32 are about farming and so on. At least I guess so.

I gathered from their talk that agrarian societies without calcium from dairy would have thinner bone structure. Maybe I mixed something up though.

[Al B. Sure!]

The times that are listed are durations. So there are introductions then 11:28 is about the book, then the next 4:32 are about farming and so on. At least I guess so.

I gathered from their talk that agrarian societies without calcium from dairy would have thinner bone structure. Maybe I mixed something up though.

Yeah but that wouldn't be genetic.

[N35t0r]

it would, because they'd be genetically predisposed to use calcium for other, more important stuff...

[Al B. Sure!]

No it doesn't add up though. Same thing as with Amerindians not having especially thick skulls (as far as I know) but never having developed helmets is a criticism for the claim that helmets lowered the selection pressure for thicker skulls.

With calcium, why is it that rates of lactose intolerance is nearly 100% among Sub-Saharan Africans yet I've always read that 'Negroids' tend towards bigger bone structure and have far lower rates of osteoporosis than Whites and Asians?

[Al B. Sure!]

By the way, with the skull issue, the other things, besides helmets, that Cochran mentioned that may have contributed to higher survival of those predisposed for less thick skulls included a change in warfare towards 'distance' warfare with the invention of the bow and, presumably, throwing spear, and the organization of government having lowered the incidence of violence (and probably distributed it from population-wide to a warrior class).

Like with helmets, these don't add up, though. Yes, the thick-skulled Aborigines didn't develop helmets and the government didn't monopolize and limit violence but they did having ranged weapons (such as the Woomera throwing spear); the Amerindians don't have thicker skulls though they also didn't develop helmets and most ethnic groups didn't develop government, though they had ranged weapons.

[N35t0r]

No it doesn't add up though.

How so? I'm not going to bother to look up all the things calcium is important for, but it stands to reason that cultures with lower access to calcium would tend to use up less for not-critical stuff, whereas with a high-calcium diet, genes for thicker bones would be selected for, since it'd end up with stronger people.

With calcium, why is it that rates of lactose intolerance is nearly 100% among Sub-Saharan Africans yet I've always read that 'Negroids' tend towards bigger bone structure and have far lower rates of osteoporosis than Whites and Asians?

I wouldn't really know about the bone structure. I'm not claiming that it is so, only that it makes sense. There might be other reasons for bone density.

Osteoporosis has several factors that cause it, and calcium intake is only a small part of it.

[Al B. Sure!]

I'm saying lactose intolerance among sub-Saharan Africans implies that diary was never a significant part of their diets (confirmed by anthropological knowledge of African diets) because there was no selection pressure for it whether it arose by a mutation or from mixture with Arabs/Berbers/whoever. So you have large agrarian, non-dairy populations all throughout Africa yet they don't have lighter bone structure and I could be wrong but Africans tend towards thicker bone structure than most other human populations (maybe someone like Hera can confirm this from non-racist sources but I'm not having much luck googling it).

My point with osteoporosis is that Africans have extremely low risk for the disease relative to whites and Asians. Consider, from Wikipedia, "The underlying mechanism in all cases of osteoporosis is an imbalance between bone resorption and bone formation. In normal bone, there is constant matrix remodeling of bone; up to 10% of all bone mass may be undergoing remodeling at any point in time."

If, as you claim, the lack of dietary calcium from dairy would favor those predisposed towards lighter bones (so less crucial calcium devoted to maintaining bones; so the balance between bone resorption and formation is different from individuals in a dairy-possessing culture), then how can it be that osteoporosis is more common among dairy-consuming, lactose tolerant whites as well as non-dairy, intolerant Asians than among non-dairy, intolerant Africans?

As you said, those non-dairy societies made people "genetically predisposed to use calcium for other, more important stuff." (ie- bone resorption) So why is it that the rates of osteoporosis vary so significantly if diet has predisposed populations towards certain bone densities?

It's an issue of consistency. I'm saying every point this guy makes can be countered by another population with the same circumstances in terms of his supposed relevant variables yet developed different consequences. To me, that must mean that those variables aren't the definitive reasons for such things as thicker skulls in some populations or thinner bones in others.

[Al B. Sure!]

Obviously, I'm no where near as learned as this guy and I probably ought to read his book to understand all his arguments, but something like human skulls becoming lighter due to the wearing of helmets in warfare just strikes me as something that would be laughed at in academic circles. Does that sound right?

[Al B. Sure!]

Anyway he is not Pashtun, he is genetucally basically Gujarati with significant East Asian admixture..

I said Pashtun because the surname Khan is more common among Pashtuns than other South Asian groups (interestingly enough, I once had a teacher named Khan and he claimed Hungarian descent and looked pretty European).

This guy's genetic history is a little odd. He says he learned Bengali when he was little (and so he's presumably Bengali which would, because Bengali are from the very east of India, jive with his claims in the article of knowing he had some sort of Burmese ancestry and his genetic profile confirmed East Asian ancestry) but the Gujarati people are in the very west of India, near modern-day Pakistan. His ancestors must have gotten around.

[N35t0r]

If, as you claim, the lack of dietary calcium from dairy would favor those predisposed towards lighter bones (so less crucial calcium devoted to maintaining bones; so the balance between bone resorption and formation is different from individuals in a dairy-possessing culture), then how can it be that osteoporosis is more common among dairy-consuming, lactose tolerant whites as well as non-dairy, intolerant Asians than among non-dairy, intolerant Africans?

As you said, those non-dairy societies made people "genetically predisposed to use calcium for other, more important stuff." (ie- bone resorption) So why is it that the rates of osteoporosis vary so significantly if diet has predisposed populations towards certain bone densities?

Because osteoporosis has little to do with calcium consumption. The main risk factors are being old and being female, and stuff like tobacco has a huge negative effect. There are tons of things that affect calcium absorption by the body, and it might be those that justify the difference. It might also mean that they are more efficient at combating bone resorption, whereas we aren't, and that our bone formation rate starts higher than theirs, and goes down more drastically. I don't really know, but there might be thousands of reasons explaining why whites are more predisposed to having osteoporosis than diet calcium content.

It's an issue of consistency. I'm saying every point this guy makes can be countered by another population with the same circumstances in terms of his supposed relevant variables yet developed different consequences. To me, that must mean that those variables aren't the definitive reasons for such things as thicker skulls in some populations or thinner bones in others.

I haven't heard the interview, so I couldn't comment on this.

[Heraclitus]

I can't sit here and listen for an hour but I tried to go to the times on some of the points, but the times don't seem to be right. They're not talking about helmets at 06:23.

Yeah I sat through the whole thing in one go and didn't notice this:

The times that are listed are durations. So there are introductions then 11:28 is about the book, then the next 4:32 are about farming and so on. At least I guess so.

[Felch]

Could hunters get calcium from bone marrow, or some similar hunting related source? I mean, is there a reason why a lactose intolerant population would get more calcium from hunting than from farming?

[Al B. Sure!]

Hera, what? Are you ignoring my counter-points?