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3. Not so thrifty diabetes genes > Disequilibrium and Metabolic Syndrome

Disequilibrium and Metabolic Syndrome

A possible explanation for the increase in resistance factors is that there has been selection against the disease of diabetes. This seems unlikely since until recently it was not prevalent enough to affect reproduction with the necessary selection intensity. Perhaps there is selection involving a more subtle aspect of diet, and the impact of diabetes incidence is a side effect of this. Alternatively, the regulation of metabolism may be so complicated, involving hundreds of genes each with a variety of alleles, that it is inevitable that the network malfunctions in some people after a few key components of the system change.

One of the central ideas of this book is that humans are now outside their normal buffering zone. Instead of thinking of some optimal body mass or blood glucose level, we ought to be thinking of well-buffered systems of interactions that keep weight and energy within a critical range in the face of a constantly shifting environment. On this view it is absolutely critical that there be genetic variation to absorb the environmental insults that any organism faces: seasonal food sources, droughts, famines, illness, pregnancy, and growing old. They all put pressure on our metabolism, and it pays to have a flexible response.


  

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