> … it made sense for humans to be lactose-intolerant as adults > Nature's solution was … What made sense for an individual human is for everyone to be lactos

> … it made sense for humans to be lactose-intolerant as adults > Nature's solution was … What made sense for an individual human is for everyone to be lactose-intolerant except them. This is what gives the best results for the individual in the near-starvation scenario. Your suggestion sounds very much like “group selection”, an idea with many high-profile detractors (http://en.wikipedia.org/wiki/Group_selection http://en.wikipedia.org/wiki/Group_selection ). The only argument I read against it was in “The Selfish Gene”, but according to the Wikipedia page, I could have picked from other high-profile scientists. Something looking like group selection may work in some cases (“The Selfish Gene” itself describes John Maynard Smith's counter-proposal of Evolutionary Stable Strategies), but offering such an explanation as obvious amounts to ignoring a lot of debunking by many bright people.