Diet and the evolution of human amylase gene copy number variation.
Starch consumption is a prominent characteristic of agricultural societies and hunter-gatherers in arid environments. In contrast, rainforest and circum-arctic hunter-gatherers and some pastoralists consume much less starch. This behavioral variation raises the possibility that different selective pressures have acted on amylase, the enzyme responsible for starch hydrolysis. We found that copy number of the salivary amylase gene (AMY1) is correlated positively with salivary amylase protein level and that individuals from populations with high-starch diets have, on average, more AMY1 copies than those with traditionally low-starch diets. Comparisons with other loci in a subset of these populations suggest that the extent of AMY1 copy number differentiation is highly unusual. This example of positive selection on a copy number-variable gene is, to our knowledge, one of the first discovered in the human genome. Higher AMY1 copy numbers and protein levels probably improve the digestion of starchy foods and may buffer against the fitness-reducing effects of intestinal disease.
Perry
George H
GH
School of Human Evolution and Social Change, Arizona State University, Tempe, Arizona 85287, USA.
Dominy
Nathaniel J
NJ
Claw
Katrina G
KG
Lee
Arthur S
AS
Fiegler
Heike
H
Redon
Richard
R
Werner
John
J
Villanea
Fernando A
FA
Mountain
Joanna L
JL
Misra
Rajeev
R
Carter
Nigel P
NP
Lee
Charles
C
Stone
Anne C
AC
D000818:Animals; D004032:Diet; D019143:Evolution, Molecular; D018628:Gene Dosage; D014644:Genetic Variation; D006801:Humans; D013213:Starch / Q000378:metabolism; D000516:alpha-Amylases / Q000235:genetics*