>>...Instead, they suggest that “Perhaps genetic development means they have the ability to tolerate large quantities of saturated fatty acids.”
There's no reason the genetic adaptation can't be the 'other' way - in the sense that there's been adaptive pressure to be able to deal with increasing quantities of carbohydrates in the diet. I've thought (no evidence) that this has been going on since the start of agriculture. We were tolerant of some dietary carbohydrates because it was used as an intermediate fuel (fats to glucose via gluconeogenesis) particularly for the CNS as neurons needed do do a *lot* of proton pumping - and the lactate astrocytes could provide from breaking down glucose made for a reservoir. So we were already equipped to make use of *some*. Agriculture meant more available calories so populations could grow - and it meant there was adaptive pressure to be able to use more carbohydrates. But it's only been a couple of thousand years, an eyeblink in evolutionary time. On top of that, only some populations have experienced this pressure since the beginning, so more variability between people in how much dietary carbohydrate they can tolerate, meaning some of us can tolerate more of it than others depending on our genetics. The T2DM epidemic in pastoral peoples changing to a more 'modern' diet seems to bear this out.
But here's the thing: just about none of us can tolerate the current 'western' diet.
Feel free to tell me I'm wrong - but tell me *why*, what factor I've missed. Like I said, this is no more than a guess. We are starting to understand what genetic variations are associated with carbohydrate tolerance. Couple that with a growing repository of DNA from human fossils and we might someday have a better understanding.