eddie:

Population genetics is fascinating, but you'll need a very solid math background to understand most of it.  I've done my best to isolate some useful takeaways.

vizeet:

I think pigmentation differences postdate all migrations out of Africa, though they may have arisen independently in Neanderthals and H. sapiens.  So it seems likely that they postdate clothes, though I don't know what evidence we have for clothing in the Pleistocene!  

Also recall that "Native Americans" are Siberians who came from Asia.  (AFAIK we're still trying to figure out if the pre-Clovis settlers were from the same population, or from somewhere else entirely.)

Population genetics is fascinating, and I didn't appreciate some of its inescapable conclusions until this series!

Kassandra:

Human pre-history is a fascinating subject.  It's rarely taught, however, for (I believe) two reasons.  First, the evidence is thinner: it's much easier to make kids memorize Egyptian dynasties than it is to talk about what the artifacts in Blombos Cave might have meant.  Second, because too many people in America refuse to acknowledge evolution.

pam:

5,000 years assumes several conditions:

It assumes that the selective advantage is extremely strong (10%).  Even frank celiac doesn't generally kill people — certainly not before reproductive age.  It makes middle and old age miserable…but lifespans in early agricultural civilizations were so low that this probably wasn't a frequent issue.

It assumes that there exists a mutation which can beneficially affect the system in question — and that it will arise when needed.  For instance, there's no single mutation that would allow humans to breathe carbon monoxide or harmlessly excrete strontium-90.  While it's apparent that frank celiac is genetically determined to some degree, there may not be any mutation which causes our intestines to ignore the effects of gliadin peptides on zonulin signaling…it may be too fundamental to our intestinal function.  And even if there is a mutation (or sequence of mutations) that would allow us to digest gliadin peptides, such a mutation is vanishingly unlikely to arise by random chance.

Furthermore, since this would be purely a biochemical adaptation, not a behavioral adaptation, the mathematics of genetic fixation I discussed in the article would come into play — which are that most beneficial mutations are lost.  Even the unrealistic 10% selective advantage is at least 80% likely to disappear, instead of reaching fixation!

All that being said, there is evidence that humans have adapted in some measure (though incompletely) to the consumption of birdseed ("cereal grains") and beans.  The longer one's ancestors have been practicing agriculture, the less common celiac disease is in a population…and on the other hand, diabetes and metabolic syndrome is rampant amongst native populations newly introduced to "Western" foods (e.g. grains and sugar).  

However, there is no evidence that zonulin signaling and intestinal permeability remains unaffected by gliadin peptides in anyone (see my second point, above) — and the nutritional profile of grains and beans is so lousy compared to animal foods that I see no reason to eat them even if they were harmless.  Also, my points about anti-nutritionism from last week's article still stand.

Bob:

What's been going on at paleohacks, and in the comments of some blogs, reminds me of junior high school.  (To your list of "gossip and ad hominems" let me add "sweeping generalizations and vitriolic attacks".)  I want no part of this race to the bottom, and I'm glad that my readers want no part of it either.  

Please keep spreading articles you find helpful, thought-provoking, or otherwise interesting, so that gnolls.org can continue to be a place of learning and thoughtful discussion.  And you'd be surprised how many others are reading "this science shit": it's just that my readers, like yourself, aren''t inclined to start or encourage drama.  I greatly appreciate that. 

Thank you for the support and encouragement!  

JS

vizeet:

If by "first migration out of Africa" you mean Homo erectus, they didn't contribute a significant proportion of the genome to India.  (The Denisovans seem to have contributed to Pacific Islanders and Australian aboriginals.)

We would expect people to show pigmentation variation based on sun exposure within a "race"...there's a difference in skin color between the average Irishman and the average Italian, though both are "white".

The hut question is interesting: one wonders how much time pre-agricultural humans would have spent in their shelters.  In the case of Bushmen the answer is "not much"...they mostly just sleep in them at night.  I think time spent indoors is mostly a post-industrial thing for anyone but the ruling elite...agricultural labor is still mostly outdoors.

Asclepius:

As the conclusion states, "This topic is far into the realm of speculation."  It's certainly entertaining speculation, though!

One central point is that fire isn't necessary to ground sleeping -- a point reinforced by accounts of the Kalahari Bushmen, who didn't require continual fire to keep lions at bay.  (This is another thorn in the side of Richard Wrangham, who maintains that we needed fire to sleep on the ground.)

Neal:

Kassandra's observations are in line with everything I've seen and heard.  Weston A. Price's "Nutrition and Physical Degeneration" was all about the problems resulting from natives adopting Western diets, and all the statistics with which I'm familiar show native populations suffering from diabetes, metabolic syndrome, and heart disease at far greater a rate than the white settlers selling it to them.

Kassandra:

Rome and Egypt would be a lot less boring if they taught the real history instead of the sanitized version, which basically involves memorizing a lot of names and dynasties and laughing at the paintings of people with animal heads.

The fundamental problem with our school system is that it was designed from the start to produce compliant manual laborers, not smart, independent thinkers -- because a nation of compliant laborers was what the ruling class thought we needed back in 1900.  

"We want one class to have a liberal education. We want another class, a very much larger class of necessity, to forego the privilege of a liberal education and fit themselves to perform specific difficult manual tasks." -Woodrow Wilson

"Ninety-nine [students] out of a hundred are automata, careful to walk in prescribed paths, careful to follow the prescribed custom. This is not an accident but the result of substantial education, which, scientifically defined, is the subsumption of the individual." -William Torrey Harris, US Commissioner of Education from 1889 to 1906

JS

vizeet:

Re: skin color, I think so.  Remember that the population genetics figures and times I cite are only applicable to the case of a mutation arising in one individual.  If there is significant genetic variation within a population in general, selection can occur much more quickly, and the variation won't go extinct due to random chance.

I've heard the same thing about India: modern diseases are rising with the introduction of modern foods.

eddie:

It depends on the reproductive rate of those with paler vs. darker skin.  I can easily see social stratification occurring, especially with the caste system (the rich get lighter, the poor get darker or stay the same)...but in America, the rich reproduce less than the poor.

JS