There is some really need speculation that Europeans white skin is a genetic adaptaion to drinking milk - here is a portion of a writing by Loren Cordain:Prevalence of Lactase in Northern Europeans
Northern Europeans and their descendants are unusual amongst the world’s peoples in that they maintain the ability to consume cow’s milk without digestive discomfort because their guts produce lactase, the enzyme necessary to digest lactose, the sugar found in milk. Between 70 to 90% of Northern Europeans maintain the adult lactase persistence (ALP) gene, whereas the presence of ALP in most of the world’s people is much lower, ranging from approximately 3 to 25 % (Figure 1)28.
Figure 1. The percentage of some world’s people with the ability to digest lactose in milk.
The standard evolutionary explanation for the presence of ALP in Northern Europeans is that once they had adopted dairying, selection for the ALP genes allowed lactose in milk to be digested without gastrointestinal disturbances and diarrhea. Consequently, ALP enabled calcium and other nutrients in milk to be readily digested, thereby enhancing nutrition and increasing survival28. One of the problems with this explanation is that many of the world’s societies with long histories of dairying, such as the Mongols, the Herero, the Nuer, the Dinka, the Zulu and the Xhosa have low levels of the ALP gene and are generally lactase deficient28, 29. These people have taken a behavioral approach to reduce the lactose in milk by consuming it as fermented products (sour milk, kumis, and yogurt) or as cheese. Certainly, Northern Europeans could have taken this approach. So the evidence suggests that the selection for ALP in Northern Europeans must have occurred for reasons other than the additional calcium and food calories found in fermented milk products.
Extreme Dermal Depigmentation in Northern Europeans
In addition to maintaining a high frequency of ALP, Northern Europeans are unique amongst the world’s people in that they exhibit extreme dermal de-pigmentation. Blond or red hair, very light skin and blue or gray irises are external characteristics that rarely occur together in any other people of the world. The standard evolutionary explanation for extreme dermal de-pigmentation is that Northern Europeans resided at high latitudes where sunlight was seasonally restricted causing impaired vitamin D metabolism30, 31. Accordingly, the selection for light skin enhanced vitamin D synthesis during brief periods of sunlight exposure in these high latitude, sunlight compromised people. The problem with this explanation, as has been previously pointed out, is that other world’s people living at similar or higher latitudes have not evolved extreme dermal depigmentation32 as depicted from the Biasutti map below (Figure 2).
Figure 2. The Biasutti map depicting skin pigmentation in the world’s peoples29.
Putting It All Together: The Bigger Picture
The reason why Northern Europeans evolved extreme dermal de-pigmentation was two fold. First vitamin D metabolism was slightly compromised in these people from reduced sunlight exposure by living at higher latitudes. But more importantly, regular consumption of whole wheat, because of its high WGA content, pushed vitamin D metabolism to the breaking point, likely causing an epidemic of rickets during the Neolithic. Remember that WGA gets into the bloodstream by binding the EGF-R, and then impairs vitamin D metabolism by blocking the nuclear pore, thereby preventing vitamin D from doing its job. So, one evolutionary strategy employed to overcome WGA’s deleterious effect upon vitamin D metabolism was to select genes coding for lighter skin so that more vitamin D could be synthesized during intermittent sunlight exposure.
The second evolutionary strategy taken by natural selection was to reduce or impair the uptake of any WGA that was ingested from wheat. This is where the selection for the adult lactase persistence (ALP) gene comes in. Raw cow’s milk is a rich source of epidermal growth factor (EGF) and contains 325ng per ml33. In contrast, the processing of milk to make fermented milk products will greatly reduce or destroy EGF as it is unstable when exposed to heat, light and acidity33-35. By ingesting raw cow’s milk Neolithic people would be directly dosing themselves with EGF which then could compete with and displace WGA for the EGF-R. Further, EGF from cow’s milk would facilitate gut healing to reduce the number of EGF receptors elicited by the destructive effect of WGA on the gut lining. The net effect of additional EGF from cow’s milk would be to impede entry of WGA into the bloodstream thereby improving vitamin D metabolism, which in turn would reduce the incidence of rickets.
Neolithic individuals bearing the ALP genes would gain selective advantage over those who didn’t have this gene because they could drink EGF containing cow’s milk without gastrointestinal discomfort. Consequently, over the course of hundred of generations, there would have been a rapid selection for the ALP genes, not because the calcium and food calories in milk provided crucial nutrition, but rather because the EGF in milk countered the rickets producing effects of WGA from whole wheat consumption. Thus, the extreme dermal depigmentation and high prevalence of the lactase enzyme in Northern Europeans were caused by the same negative selective pressure: high consumption of WGA containing whole wheat. Perhaps there are additional lessons to be learned by us all from this 10,000 year evolutionary experiment in eating whole grains.
"Perhaps there are additional lessons to be learned by us all from this 10,000 year evolutionary experiment in eating whole grains."
Yes, don't eat them. Or if you are going to eat them, drink raw milk? :)
Cordain's thoughts are very interesting. I had been under the impression that latitude was sufficient to explain lightened skin color. It would have been helpful to see Figure 2, but I think I'd need more detail than that to be convinced. I'd want to know, for example, how long the non-depigmented populations have been living at northern latitudes, how their lifestyles compared to those of lighter-skinned Northern Europeans, how their diets compared, etc.
However, he's making me cringe with all the "ALP gene" talk. He means adult lactase persistence allele, not gene. Alleles are forms of genes. People who can digest lactose in adulthood don't have extra copies of a modified lactase gene. They simply have a variation of the gene (an allele) that allows continued production of lactase in adulthood.
The use of fermented dairy makes sense to me. Seems that fermented/sprouted/soaked grains are more tolerable to many human's as well. Weston A Price Foundation stuff all around!
I experimented with soaked/sprouted/fermented grains in the past, and had success with it, no real obvious pitfalls. But a bit more reading on grains' potential harm to our auto-immune system and gut had me swear off them. Once I did, I had a marked elimination of joint pains AND my seasonal hay fever/allergies vanished. It's all stayed that way for quite some time now, so I'm taking it as cause and effect.
That, and all that prep time to use grains in the WAPF manner is too much for me. I'm too lazy it would seem.
Thanks for the bit about "alleles vs. genes" Pikala. Seems I learned that back in high school? but forgot. Details like this are pretty important it would seem. It shows the step to utilize lactose late in life is NOT a huge evolutionary step as evolving to grains might one day require! If we should ever get there.....
Thanks, Pikaia - you did a better job than I did explaining the lactase enzyme allele. I am used to explaining evolution to 10th graders and sometimes I have to start simply than add the details later. Love your posting name, by the way. I wonder how many know what Pikaia is? One of my favorite Cambrians :)
Hahaha, Katt I like your perspective! My heads always in the clouds so when I look down puddles often look like ponds. Oh and I stumbled across this whilst surfing, it posses the theory that switching to a cereal based diet, along with other factors, during the neolithic era has led to our improved life expectancy now. http://18.104.22.168/search?q=cache:cKzL_WXogjcJ:www.iadb.org/res/includes/pub_hits.cfm%3Fpub_id%3Dp-881%26pub_file_name%3DpubP-881.ppt+ability+to+tolerate+gluten+in+humans&cd=3&hl=en&ct=clnk&gl=uk
Evolution, definitely one of the stranger systems in nature ey!