evolution of milk drinking

[Guest guest]

FYI, I spotted this article on the evolution of lactose tolerance on

the Scientific American site:

August 28, 2009 | 7 comments

Did Lactose Tolerance First Evolve in Central, Rather Than Northern

Europe?

Tolerance for cow's milk may have arisen in the Neolithic period among

the Linearbandkeramik culture of central Europe, not with the Lutefisk-

lovers of Scandinavia

By Lynne Peeples

Dairy farmers living in Central Europe around 7,500 years ago may have

been the first human adults to drink cow's milk—at least comfortably.

Integrating genetic and archaeological data, Mark and

colleagues at University College London were able to trace down the

first evidence of lactase—the enzyme that allows us to digest the

complex milk sugar lactose—persisting beyond the weaning years into

adulthood to " exactly when you see the beginning of Linearbandkeramik

culture [considered the firstNeolithic society in Europe], "

says. " When that started, you saw a change from a mixed economy to one

based primarily on cattle. " And, with this revolution, came a strong

evolutionary advantage for people able to consume milk and its

nutrients without digestive discomfort.

Before the evolution of lactase persistence, humans typically lost

their ability to digest lactosearound the age of five. (This is

thought to have helped motivate weaning.) Still today, most of the

world's population can only tolerate milk for the first few years of

life. But, through at least four parallel evolutions starting several

thousand years ago, lactase persistence spread throughout human

populations. One of these, the earliest, is known to have originated

in Europe.

The genetic mutation conferring this advantage—shared by most lactose

tolerant Europeans—was commonly thought to have occurred first in the

northern part of the continent, where the sun shines less and people

may be in greater need of the vitamin D found in cow's milk. (Sunlight

is human's main source of vitamin D, which is necessary for the body's

uptake of calcium.) But 's new research published today in the

journal PLoS Computational Biology begs to differ.

and his colleagues note the trait started farther south before

spreading to the north, according to the results of their computer

simulation model. " I suspect there are two important factors

[triggering the evolution of lactase persistence]: consistency in

supply and contaminated fluids, " says.

Pioneer farmers made their way north with domesticated crops from the

Near East, he explains, but these crops were not necessarily well

suited for the new environment. So, as the pioneers found themselves

isolated with only feeble crops and cattle as well as parasite-ridden

water sources, cow's milk may have become an increasingly important

staple for survival. " Seasonal crops are boom and bust, but cattle

provide food even when crops are failing, " says. " The only

problem is you must be able to drink it. " Those on the brink of

starvation, he notes, would not have been able to survive the diarrhea

that lactose intolerance brings.

Of course, there are other (less probable) ideas still being milked:

points out one example—that tolerance evolved as " prestige " via

" Neolithic drinking games " : men battling it out to drink a quantity of

milk without getting sick. " Like football players, maybe they screamed

at each other while downing one, " says. " Then some guy comes

along, doesn't get sick, and everyone thinks he's cool. " One has to

wonder, did the macho milk drinker then rub it in his opponents' faces

by chanting, " Got milk? "

http://www.scientificamerican.com/article.cfm?id=lactose-toleraence