Michael Hammer at the University of Arizona in Tucson tracked the DNA of three separate populations and found there was less variation in the male chromosome DNA. His findings, published in Nature Genetics, suggest that over the years half as many men as women have passed on their genes.
[F]emales also tend to be similar in their tastes, which means some males get chosen far more often than others, and therefore have more offspring. Females, by contrast, tend to have about the same number of offspring each.