Throughout human history, relatively few men seem to have had a greater input into the gene pool than the rest, suggests a study of variations in DNA.
Tens of thousands of years of polygamy has left a mark on our genomes that is a signature that small numbers of males must have mated with lots of females.
Over time, such a pattern will spawn more genetic differences on the X chromosome than other chromosomes. This is because women have two copies of the X, while men only one. In other words, the diversity arises because some men don鈥檛 get to pass on their genes, while most women do.
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鈥淗umans are considered to be mildly polygynous and we descend from primates that are polygynous,鈥� says , a population geneticist at the University of Arizona in Tucson.
Polygyny refers to the practice of males mating with multiple females, and its most common form in humans is polygamy or multiple marriages.
To find our hidden genetic history, Hammer and his colleagues sequenced DNA from 90 people belonging to six groups: Melanesians, Basques, Han Chinese, as well as three African cultures: Mandenka, Biaka and San.
Long tradition
Hammer鈥檚 team discovered more genetic differences in the X chromosome than would be expected if equal numbers of males and females tended to mate, over human history. The only explanation for this pattern is widespread, long-lasting polygyny, he says.
His team鈥檚 analysis reflects all of human history, and modern monogamy has not even left a blip in our genomes. 鈥淚 don鈥檛 know how long monogamy has been with us,鈥� Hammer says. 鈥淚t seems it hasn鈥檛 been around long, evolutionarily.鈥�
Besides, 鈥渕ost societies practice some form of polygamy鈥�, he says. Even if most Western men don鈥檛 take multiple wives, men tend to father children with more females than females do with males, a practice called 鈥渆ffective polygamy鈥�.
鈥淚t鈥檚 not unexpected,鈥� says , an evolutionary geneticist at Stanford University in California. 鈥淧olygany is something you would expect to find.鈥� Petrov and his colleagues uncovered the same genetic pattern in fruit flies.
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