Well, as another datapoint to study, asians are said to have a near 90% adult lactose intolerance rate. So whatever beneficial natural selection for Europeans that propagated the always-on lactase mutation, the same cultural/agricultural circumstances didn't hold true for asians.
> "asians are said to have a near 90% adult lactose intolerance rate"
I'm very skeptical of this. I was born and raised in Asia, and all of my peers were raised on a diet with regular milk consumption. So either we were a huge cohort of statistical outliers or that number is way, way off.
I do know that lactose intolerance rates for Asians is much higher (and consequently, less socially troublesome due to the fact that dairy is generally not a core part of cuisine), but 90% is way, way, way out there.
+1 to that. Among all the people I've ever known (in India) only 2 people are lactose intolerant. Indian society has, historically, placed a lot of importance on the cow and milk. Indian mythology has rich references to milk and other dairy products for eg. Samudra Manthan [1], Krishna the cowherd [2]. If we were to consider the level of medicine practiced in India (see [3] and [4], for eg.), one would imagine that any real problem of such widespread nature would be heavily studied and discussed about.
And Australian. "Asian" to me has always meant: China/Japan/Malaysia/Indonesia/Korea(s)/Thailand/Vietnam/Phillipines/PNG/Timor/Laos/Cambodia and maybe Burma.
I've seen these numbers but my experience in Asia (South Korea and Eastern Russia) seems to be the opposite. Milk is not heavily consumed in South Korea, but I've yet to meet more than one or two people who can't drink it.
All of the Indians I know are fine with milk and my understanding is that milk is now part of the regular childhood diet in Japanese school lunches [1].
Anecdotally, I do know a few Chinese Americans who grew up in the U.S., moved to Hong Kong during their middle and highschool years, didn't tough the stuff while there and came back lactose intolerant as adults. So I suppose it may be an acquired skill one has to keep up with? (their younger siblings who didn't make that trans-pacific journey are fine with milk)
Anecdotally, this seems untrue. I was back in China for 2 months earlier this year and milk (fresh, no less, with expiration days of literally 3 days or less) are sold everywhere. Clearly there is a high demand for milk in mainland China (so much so that there are even brands of imported milk from Germany). This was in the capital of Beijing.
Actually, a little more looking, I think I also found the Yale study it's from. Here's the power point: http://cst.yale.edu/sites/default/files/worldwide distribution of lactose intolerance, madison 2010.pptx
Perhaps the difference is due to the fact that East Asians domesticated different kinds of cereal crops than Europeans did. Perhaps milk wasn't as important in a rice-based diet as it was in a wheat-based diet? (But then again, Indians eat rice and they're lactose tolerant according to the article.)
Or perhaps East Asians developed different kinds of social and economic structures that mitigated the disadvantage of not being able to consume milk.
Or perhaps the necessary mutations just didn't get incorporated into East Asian genes. Also according to the article, the lactose tolerance gene spread as far as India but didn't cross the Himalayas.
Indians started cultivating rice (~ 2000 B.C.) much later than the Chinese (~ 4000 B.C.) [1]. Given the rate at which lactose tolerance spread in Europe, Indians had already developed lactose tolerance by the time they started cultivating rice.
In China I heard that many older Chinese people can't drink milk, but the younger generation (who've drank it all their lives) can. Apparently there were lots of parents who couldn't drink milk themselves who would go to the "milk shop" every week to stock up for their kids. (The place I lived had this little store that just sold packets of milkshake and cartons of UHT milk).
