Posted on 06/01/2005 5:15:57 PM PDT by PatrickHenry
A new Cornell University study finds that it is primarily people whose ancestors came from places where dairy herds could be raised safely and economically, such as in Europe, who have developed the ability to digest milk.
On the other hand, most adults whose ancestors lived in very hot or very cold climates that couldn't support dairy herding or in places where deadly diseases of cattle were present before 1900, such as in Africa and many parts of Asia, do not have the ability to digest milk after infancy.
"The implication is that harsh climates and dangerous diseases negatively impact dairy herding and geographically restrict the availability of milk, and that humans have physiologically adapted to that," said evolutionary biologist Paul Sherman, a professor of neurobiology and behavior at Cornell. "This is a spectacular case of how cultural evolution -- in this case, the domestication of cattle -- has guided our biological evolution."
Although all mammalian infants drink their mothers' milk, humans are the only mammals that drink milk as adults. But most people -- about 60 percent and primarily those of Asian and African descent -- stop producing lactase, the enzyme required to digest milk, as they mature. People of northern European descent, however, tend to retain the ability to produce the enzyme and drink milk throughout life.
Sherman and former Cornell undergraduate student Gabrielle Bloom '03, now a graduate student at the University of Chicago, compiled data on lactose intolerance (the inability to digest dairy products) from 270 indigenous African and Eurasian populations in 39 countries, from southern Africa to northern Greenland. Their findings will be published in a forthcoming issue of Evolution and Human Behavior.
On average, Sherman and Bloom found that 61 percent of people studied were lactose intolerant, with a range of 2 percent in Denmark and 100 percent in Zambia. They also found that lactose intolerance decreases with increasing latitude and increases with rising temperature, and especially with the difficulty in maintaining dairy herds safely and economically.
A major challenge in interpreting the data, Sherman noted, was to resolve the puzzle that about 13 lactose-tolerant populations live side-by-side with lactose-intolerant populations in some parts of Africa and the Middle East.
"The most likely explanation is nomadism," Sherman concluded. All 13 of the populations that can digest dairy yet live in areas that are primarily lactose intolerant were historically migratory groups that moved seasonally, Sherman said. Their nomadism enabled them to find suitable forage for their cattle and to avoid extreme temperatures. "Also, the fact that these groups maintained small herds and kept them moving probably reduced the pathogen transmission rate."
According to the National Digestive Diseases Information Clearinghouse, some 30 million to 50 million Americans are lactose intolerant, including up to 75 percent of African Americans and American Indians and 90 percent of Asian Americans. Common symptoms include nausea, cramps, bloating, gas and diarrhea that begin about 30 minutes to two hours after eating or drinking foods containing the milk sugar lactose. The use of lactase enzyme tablets or drops or lactose-reduced milk and similar products can help the lactose intolerant digest dairy products.
Sherman's study concludes that adults from Europe can drink milk because their ancestors lived where dairying flourished and passed on gene mutations that maintain lactase into adulthood. The research, he said, is an example of Darwinian medicine, a new interdisciplinary field of science that takes an evolutionary look at health, and considers why, rather than how, certain conditions or symptoms develop. Sherman, for example, recently investigated why spices are used and why morning sickness occurs.
"Both appear to serve an important function to protect the individual," Sherman said. "Spices contain antimicrobial compounds, and they may be used to destroy food-borne pathogens, especially in hot climates. Nausea and vomiting early in pregnancy also may protect women and their embryos from food-borne pathogens and other toxins."
A Darwinian medicinal view complements traditional medicine, Sherman said, because if researchers can better understand why a symptom occurs, such as a fever, runny nose or allergy, they can better evaluate whether it is best to eliminate or tolerate it.
Darwinian medicine. Something new to think about. Everyone be nice.
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Most Chinese are lactose intolerant and China doesn't fit this scenario at all. So I guess Darwinianism doesn't apply to 1/5 of humanity.
Never heard of this new medicical discipline before. My first impression is it is perilously close to Lamarckian Evolution. Guess it is time to google.
Are there any native cattle (or other milk producing animals) which were dometicated in China? If not, then ability to digest lactose wouldn't be a survival benefit. On the other hand, if you have a Germanic tribe where Johann's family can drink milk but Wilhelm's family can't, that could be the difference between living and dying during a tough year growing crops.
I don't know about all of this, but I am descended from Scottish, English, French, and German ancestors, all of whom are part of the dairying peoples, and I am lactose intolerant, as is my father, and at least one of my nieces.
Pure and Simple B.S.
My family is from Poland, They came to America and settled in Wisconsin, owned dairy farms. If I drink a glass of milk I cramp and (other things I would rather not mention) for days.
1. Fermented milk products have had the lactose removed.
2. Lots of people are lactose intolerant, most specifically Asians. The biochemistry is simple. As an infact the enzyme beta-galactosidase operates to split lactose to glucose and galactose. In adult life a new enzyme appears, lactase that also cleaves lactose. The beta-glalctosidase levels drop. People who are lactose intolerant don't make much lactase, but the bacteria in their intestinal tracts love it, so it gives you intestinal problems.
Bugs 1, people 0
A similar Darwinian explanantion should apply to the effects of alcohol on Native Americans.
Wonder what is different between cow's milk and goat's milk? My father in law was so intolerant of cow's milk, he was weened on goat's milk. He wsas from Germany.
My family is from Poland, They came to America and settled in Wisconsin, owned dairy farms. If I drink a glass of milk I cramp and (other things I would rather not mention) for days.
Not B.S.
My family is from Poland, They came to America and settled in Pennsylvania and New Jersey, and consumed a lot of dairy products. If I drink a glass of milk, I don't cramp, but enjoy every drop of that homogenized dairy goodness. Cheese and Ice cream, too. MMMMmmMMm.
The Bantu people arose in equatorial and West Africa, true, but they certainly have not had cattle since 'time immemorial'. Cattle were introduced from the north probably around 100 AD.
BTW, fermenting it destroys the lactose.
Fascinating. What a stunning reproof of ID. Their already hyper-strained arguments must now be further strained by the insistence that this only suggests God "created" different groups' ability to metabolize milk according to the groups' proximities to dairy-friendly regions.
I live in Southeast Asia where, at least, the majority of my friends and in-laws are lactose intolerant. To my knowledge, Tibet and Mongolia are the exceptions to the no milk products tendency of this part of the world. It would interest me to know the results of such a study in those areas. I know that in Chiang Mai, while people love ice cream, most cannot handle much and many cannot handle any. BTW the Dairies and cheese makers are all German.
A Google search reveals that you're on to something:
Forbidden fruit: understanding alcoholism in the context of evolution.
What about the Zulu's that drink blood.
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