Carl Zimmer on The Evolution of Cavities

Carl Zimmer on The Evolution of Cavities:

… The Streptococcus mutans the scientists found in people’s mouths shared 1490 genes in common–a core genome, as it’s known. These shared genes varied from mouth to mouth, Stanhope found, with minor mutations sprinkled among them. It’s possible to tally up these mutations and use them to reconstruct some of the history of their ancestors. Stanhope and his colleagues found that Streptococcus mutans underwent a population explosion. And that explosion started ten thousand years ago.

It may well be no coincidence that this was also when our ancestors began to farm. Those early farmers shifted to diets dominated by corn and other grains–which turned the human mouth into an endless banquet of carbohydrates.

Stanhope and his colleagues were also able to pinpoint some of the genes that were important forStreptococcus mutans’s adaptation to civilization. Fourteen genes, for example, show signs of having experienced strong natural selection. Some of those evolved genes are essential for breaking down sugar. Others help the bacteria survive in the acidic conditions that arise in the mouth when we eat starches.

…

So Streptococcus likes our farming. Hmm.