Did Lactose Tolerance Trigger the Indo-European Expansion?
Agriculture allowed those who practiced it to greatly expand their numbers, but it is distinctly possible that the nutritional quality of the food of early farmers was initially worse than that which had traditionally been available to hunter-gatherers. Consequently, the health of each individual was not necessarily better in the Neolithic period than it had been in the Paleolithic era. The bodies of those who practiced agriculture had to adapt to a new diet consisting of foods that had either not been eaten before or had previously been of only minor importance.
According to The 10,000 Year Explosion, “For example, we see changes in genes affecting transport of vitamins into cells. Similarly, vitamin D shortages in the new diet may have driven the evolution of light skin in Europe and northern Asia. Vitamin D is produced by ultraviolet radiation from the sun acting on our skin – an odd, plantlike way of going about things. Less is therefore produced in areas far from the equator, where UV flux is low. Since there is plenty of vitamin D in fresh meat, hunter-gatherers in Europe may not have suffered from vitamin D shortages and thus may have been able to get by with fairly dark skin. In fact, this must have been the case, since several of the major mutations causing light skin color appear to have originated after the birth of agriculture. Vitamin D was not abundant in the new cereal-based diet, and any resulting shortages would have been serious, since they could lead to bone malformations (rickets), decreased resistance to infectious diseases, and even cancer. This may be why natural selection favored mutations causing light skin, which allowed for adequate vitamin D synthesis in regions with little ultraviolet radiation.”