Brewer's yeast may have been the first species cultivated by humans.

Scientists constructed an evolutionary tree for yeast based on the genes of yeasts found in different foods. The yeasts in beer, wine, sake and other fermented drinks and foods are different from each other.

Differences among varieties of yeasts reflect their different roles. Yeasts that ale brewers use tend to rise up out of the liquid by clumping onto the carbon dioxide they produce. Malt beer yeasts have extra copies of the genes associated with breaking down maltose, the main source of carbon in malt.

Bread yeasts divide quickly to carbonate dough in the shortest amount of time possible. This fast action produces more odd flavors and so they have been avoided in wines and beers.

Yeast genes reveal the story not just of brewing but also of domestication, the product both of natural selection and civilization.

Beer yeasts evolved early. The evidence of beer gardening based on the yeast evolutionary tree is roughly as early as the evidence of wheat farming.

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