From New Scientist: Polygamy left its mark on the human genome.
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’t get to pass on their genes, while most women do. [continue]
Methinks polygyny has always be a perogative of the powerful. Plus extreme poverty, disease and early death (the lot of the common man) a co-indicator of reduced fertility/death in childbirth/high incidence of death in childhood. Being the progeny of a powerful man (legitmate or not) would be a better prognosis for survival and passing on the genes. Makes sense to me.