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That was exactly what I was thinking. Lactose tolerance is a very recent biological evolution, so much so that there can be marked differences within an individual population. For instance, there's 30% more lactose intolerance in the South of France than in the North of France. It seems to be a trend that in the Medetarranian areas where fishing is more readily available throughout the year that lactose intolerance is higher. Despite a very short geographical distance, the percentage differences are huge. Sicilians for example have ~70% intolerance, Italy on average has ~35% tolerance, while just over the border in Switzerland you're down to 10%. The differences can also be seen within a very, very short geographical range. For instance the Basques, a Spanish population historically centred around the Pyrenees (mountains) have the lowest intolerance in the world at 0.3%, while the non-basque Spanish have 15% tolerance, literally from not living on the herding steppes. The latest period at which Native Americans could have migrated is at 12,000 years ago. In this period of time they have acquired zero lactose tolerance. However in the same time period, the Siberian peoples who the Native Americans came from became lactose tolerant. Assuming the highest rate posted for Russians their lactose intolerance is ~60%, however this is a dubious figure considering population exchanges between the Mongolian and Siberian populations (they're a political divide on a single Eurasian Steppe, it seems highly doubtful that genes would have stopped their spread for our political niceties 2,000 years in the future). Assuming the Mongolian percentages, Siberians likely now have a lactose intolerance rate in the single digits. This compares to the non-steppe population in 'Inner Mongolia' (China) who hit at about 87% intolerance. With the vast divide between lactose tolerance on such an incredibly short scale of time and distances, I highly doubt we wouldn't have evolved some sort of gluten tolerance, especially considering the vastly higher percentages of lactose intolerance compared to gluten intolerance. Let's put it this way, unless you're a Spanish Basque, your greatest concern for adverse health effects in a sustainable diet is dairy. The Dutch, Swedes and Mongolians of the Steppe are the next to be concerned. Anyone else, be concerned when your doctor diagnoses you, because otherwise you're as dumb as a dog chasing its tail. |