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Analysis of fossilized bones suggests milk-drinking mutations emerged after dairy herding.
When did ancient populations learn that drinking milk 'does a body good'? A team of scientists in Germany has tried to answer this question by studying ancient DNA extracted from skeletons thousands of years old.
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Posted by Nicola Jones on February 26, 2007
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This is very interesting research. There really was not much of a controversy ... no one has expected the adaptation to arise prior to the condition by which it is selected ... but a finer look at how long it took to develop will be very useful. I've got some comments on this general issue here:
http://gregladen.com/wordpress/?p=422
Posted by: Greg Laden | February 28, 2007 12:27 AM
Is it a question of human mutation to digest lactose, or the bacteria that digest lactose?
Posted by: Mike Swanton | February 28, 2007 01:26 AM
herding dairy cattle and milk drinking will not spread the mutation. milk drinking may kill off the non dairy drinking population and remove them from the gene pool so the non drinkers reduced and the drinkers increased.
Posted by: paul Bunt | March 1, 2007 07:43 PM
Another question is what are the differences in absorption and digestibility of modern dairy? The product as a whole and the changes that have happened beginning with homogenization,then adding chemicals/antibiotics and genetically engineered feed,also hormones like rBGH and the latest news brings us cloned milk. Public comment period open until April 3rd 2007. Docket # 2003N-0573
What is our status with prions in milk?
Besides I'm in a state which is among few that are not Brucellosis and Tuberculosis free...recent news.
No mustache here.
Erica
Volunteer for centerforfoodsafety.org
Posted by: Erica Gray | March 4, 2007 02:13 AM
Mike: There is an enzyme in mammals that breaks down lactose, but that is normally not expressed in adults. That is not an enzyme in bacteria, it is an enzyme produced by the mammal (in this case human).
Paul: The lactase enzyme being produced later in life may give the individuals with that mutation an advantage if there is some milk drinking going on. (Lactaose could be for those people an important energy source, say when other foods falter). That could facilitate the spread of the mutation. Individuals who have adult lactase production have the additional energy (compared to others without the enzyme production) in those bad years, and thus reproduce while others don't (for ecample).
Posted by: Greg Laden | March 5, 2007 12:26 PM
From a layman's view it would seem most probable that the area where domestication had the longest history would be the area where the "biological anamoly" - lactose-tolerance of adults - would show the highest frequency.
The results from genetical research within todays populations shows that the caucasians of Northern Europe have the highest percentage of tolerance. Is there - btw - any map published that shows the various degrees of tolerance/intolerance among the present populations covered by the Human Genetics Project?
The next question would be wetter the early Caucasians of NW Europe have shown a better ability to adapt to the consequences of domestication than other populations - OR, if the old model of the agricultural spread; by migration rather than diffusion - actually happened, anyway, leading to the present location of the Caucasian agriculturalists.
A third possibility would be that the first domestication of animals actually developed in central Europe - rather than Anatolia/Caucasia.
**
A final question would be the reliability of this test. Other tests of ancient bones from museal store-rooms have already shown that the substance of DNA is poor and far less reliable than recently excavated samples. What was the case in this survey?
Posted by: Bo S. Olsson | March 5, 2007 07:14 PM
The highest level of lactose tolerance is among the Great Lakes of Africa people, in the vicinity of Rwanda, the eastern congo, and Burundi. The region of Northern Europe was the last place cattle and other milk producing domesticates got to in comparison to all of Europe, much of Asia, and northern and northeastern Africa.
So while it is logical that the most complete changeover to this allele in a population would be the region with the longest history, it is simply not the case.
There are three possible explanations (that I can think of right now) for this: 1) The model of time = more of a genetic change is either wrong or not strong; 2) the model does work but needs to include the strength of the natural selection ... maybe northern Europeans and Africans in the Great Lakes region were simply under stronger selection or 3) the reason for this genetic state existing has to do with something other than lactose. (That has been suggested, by Bill Durham, if I remember correctly).
Posted by: Greg Laden | March 6, 2007 04:28 PM
Very interesting research!
I read that around 75% of the world’s adults can’t drink a lot of milk. Being lactose intolerant is normal for an adult. People who can drink milk as an adult have a DNA mutation.
Posted by: Anna Kowalska | July 20, 2007 04:34 PM
I would argue that casein, and not lactose, is the primary culprit when it comes to intolerance of milk. After all, lactobacillus strains receive their name by the fact that they break down lactose into lactic acid for us. I think this "lactose intolerance" myth is best evidenced by the fact that goat's milk and products which contain the same amount of lactose, do not share the a-casein of cow's dairy, and that is why many people who can't drink cow's milk can drink the universal foster milk: goat milk.
Posted by: SAYER | July 21, 2007 01:44 AM
The next question would be wetter the early Caucasians of NW Europe have shown a better ability to adapt to the consequences of domestication than other populations - OR, if the old model of the agricultural spread; by migration rather than diffusion - actually happened, anyway, leading to the present location of the Caucasian agriculturalists.
Posted by: Bank zdjec | August 6, 2007 04:27 PM
I read that around 75% of the world’s adults can’t drink a lot of milk. Being lactose intolerant is normal for an adult. People who can drink milk as an adult have a DNA mutation.
Thank you for the useful informations.
Posted by: Apteka internetowa | August 10, 2007 12:41 AM
thx for the great article. saved it! but the comments are more important than the mainarticle :P
Posted by: Ranking | September 12, 2007 11:35 AM
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thx
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Posted by: t-shirts | October 1, 2007 05:28 AM
Interesting. I've always thought about this simple question : I mean, who looked at a cow's udders (or watched the babies at her teets) and said, “Hey, I wonder what that tastes like?” Or, “Hey, if it's good for them, maybe it's good for us too.”
It may have been as simple as the above, though, and hardly needs such a scientific explanation. Still, to know where exactly it came from can be very interesting, especially if we can figure out who those people are today (generationally.)
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