MILK MAP: The lactase molecule and Linearbandkeramik pots overlain on a map of Europe.
Image: Yael Pinchevsky, Yuval Itan, Joachim Burger and Mark G. Thomas. Photographs credit: Sabine Schade-Lindig
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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 Thomas 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 first Neolithic society in Europe]," Thomas 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 lactose around 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 Thomas's new research published today in the journal PLoS Computational Biology begs to differ.
Thomas 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," Thomas 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," Thomas 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: Thomas 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," Thomas 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?"
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17 Comments
Add CommentLet's look at this evolution of change from a different perspective. If a child can continue to digest milk after the age of 5, she will be healthier and more likely to reach the age of reproduction. Once her parents consent, or she elopes, she can reproduce. Those children, also will be healthier and able to tolerate lactose. No screaming men involved.
Reply | Report Abuse | Link to thisFurries may have been responsible for lactose tolerance! Imagine that a neolithic farmer happens to be a furry with a fetish for cows. He carefully sews himself a bull fursuit, puts it on, and begins courting the more attractive bovine members of his herd.
Reply | Report Abuse | Link to thisHe falls in love with one of his lady cattle, and (as tends to happen with mammals in love), some erotic snuggling takes place. One evening, while the furry farmer is erotically licking at his cow-bride's nipples, he gets a mouthful of cream. With a little experimentation, he learns how to milk her as a form of foreplay. His friends and neighbors are enchanted by how much in love he and his cow-wife are, and decide to also have sexy fun with the herd. Interspecies mating becomes a village tradition, so when one person has a random mutation making them lactose-tolerant, the social behavior of milk-drinking is there to allow them to take advantage of it. If that person also occasionally mated with human females as well as quadrupeds, the mutation would spread.
It's about as plausible as people going to the trouble of squeezing cow parts and drinking the stuff that came out as a competitive game.
Lemur123, what you say is very funny, indeed! Thank you!
Reply | Report Abuse | Link to thisHans L
Frozzle, exactly! They seem to ignore that the migration north would have been over a long period of time and that even if in the early stages, those having to rely more and more on milk could have suffered great losses, when weak, starving people would get sick from relying on milk, there would be those that wouldn't get so sick, that would survive and so be the ones more likely to survive to reproduce and it wouldn't take long for the lactose intolerant people in those conditions to become extinct and the rare tolerant people to have a number of generations of population growth to fill the gap.
Reply | Report Abuse | Link to thisIt's always possible that some bizarre thing in the past could be true, like the Macho Milk Men drinking to prove their will power, but that one just seems ridiculous and of course, there's no way to prove many things from that time period, so it allows people to propose their fantasies- though I wonder if they are serious or trying to pull our leg.
I have often wonderd ,when and how Europeans came to consume milk . After all it is very unnatural for any species to consume milk after it reaches adult age. The idea of drinking the food desinged to nurish another species is abhorrent and would need some great motivation to overcome.
Reply | Report Abuse | Link to thisThe last paragraph was just a parody of college kids downing beer.
Reply | Report Abuse | Link to thisI'm always amused by the way in which the mathematically inclined tend to think in absolutes. In the first place lactose intolerance is not an absolute condition. Some people are more tolerant than others, furthermore there is no mark on the calendar which determines when the enzyme lactase disappears from the GI tract of an individual.
Reply | Report Abuse | Link to thisIt is a mistake to take generalized data and ascribe definite numbers to them. All that these observations mean is that firstly some people in any population will react more dramatically to the ingestion of milk than others. It is just that the proportions of such people will vary dramatically between populations. That is what science is observing.
Secondly the unplesantness of a reaction that is not necessarily fatal is less unplesant to pastoral people living outdoors than it is to house-dwellers, also pastoral people would have easily found out, like the Masai in Africa, that the curdling of milk, not only allowed it to be preserved longer but allowed the lactose to break down on its own thus easing the problem.
Finally, it wouldn't have taken much maternal imagination for a woman with an isufficient milk supply, or some form of mamary infection, or for people caring for a child whose mother had died in childbirth, to try feeding that child with the milk from a domesticated animal, so the progression from human milk to cow's and sheep's milk is a very natural one, not requiring the childish imagining proposed in the article. But, bear in mind that there is not really any easily determined point on the calendar when ALL lactose intolerant persons suddenly lose their tolerance for milk.
I'm not convinced. Both the article and those commenting offer very reasonable theories why a population might develope lactose tolerance.
Reply | Report Abuse | Link to thisBut what is the theory that explains why lactose tolerance happened more in Europe as opposed to elsewhere in the world especially with so many good theories floating around that aren't so geographically specific (suggesting that it is perhaps as possible for lactose tolerance to have developed anywhere or everywhere instead of just in Europe)?
Even if central Europe was the only place on earth where ancient humans who herded cows struggled with feeble crops, the feeble crop theory still seems no more compelling or convincing than the theories presented by the commentors that have nothing to do with whether or not a population was in central Europe.
Perhaps it is more useful to just accept that westerners are more lactose tolerant until such time as more profound evidence is discovered as to why.
Simulations are all fine and good, but simulations just tell you one possible way in which something could have happened. Unless you run an extremely large number, they cannot tell you which is the most likely. They can never tell you which actually happened. All you can do is look at the mutation that made the enzyme possible, all subsequent mutations to that mutation and all haplogroups where the mutation is infrequent. That will give you upper and lower bounds, but it's as far as genetics can go. After that, the only information will be archaeological - residue evidence of milk or milk-based product (eg: cheese, butter, milk-based alcoholic drink) in a container, for example, or some other solid evidence of milk in actual use. Language won't help, as milk isn't invented, so it'll have been named before it was utilised. We've virtually no Neolithic European words anyway. You MIGHT find skeletal evidence, as an increase in calcium uptake would presumably alter bone composition and delay bone degenerative conditions outside the bounds technology could explain. Hair samples would clinch it, as hair will reflect digested foods and drink, but the Ice Man is the oldest source of uncontaminated human hair I know of and that's 2,000 years too late to help us. We'd need a similar find that is much, much earlier, and preferably several such finds. Anyone here going to volunteer trawling the frozen wastelands of the world in search of 7,500-year-old hair samples?
Reply | Report Abuse | Link to this"Got milk?" Don't you think this idea of competitive drinking with milk 'dumbs down' the article? It seems like a fairly improbable hypothesis.
Reply | Report Abuse | Link to thisYou don't seem to understand the process Lemur. The enzyme is not a mutation. It has always existed in milk drinking mamals. The peculiarity is its persistence in the GI tracts of European populations, in general, past the first 5 years or so into adulthood. This requires no intricate theories, since the explanation is as simple as supply and demand theory. When the supply of milk stops at weaning, the enzyme eventually disappears from the GI tract within a few years. In countries which developed an abundant supply of milk the enzymes never disappeared, because milk i.e. lactose was incorporated into the food supply. In countries where the terrain is not conducive to herding, because of parasitic infections etc. this never happened, because there was no abundant supply of milk. Seems very simple to me.
Reply | Report Abuse | Link to this/facepalm
Reply | Report Abuse | Link to this...."parents consent or she elopes..."? WHAT!? SHE wasn't born into some modern day Judea-Christian home, give me break!
Reply | Report Abuse | Link to thisThat's a molecule of lactose, not lactase, in the illustration.
Reply | Report Abuse | Link to thisYes, 10.
Reply | Report Abuse | Link to thisBTW, that molecule is lactose, not lactase.
The molecule in the little drawing is of lactose, not lac<strong>tase</strong>.
Reply | Report Abuse | Link to thisAlso, there is little to no vitamin D in (unfortified) cow's milk, so the main premise of the article (that lactose tolerance must have developed in Northern climates 'cause of the lack of sunshine) is off.
Also, amen to the stupidity of lactose tolerance being a sexually-selected characteristic, at least in the way described. A men's drinking game? Tell me that was a joke.
I'm a little disappointed, SA.
Sorry, several other people got to the "lactase" first. Also, no HTML elements... got it.
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