Scientists discovered that about 8,000 years ago, only one man reproduced for every 17 women who did.
The researchers studied DNA from more than 450 volunteers from around the world and found the number of men who passed on their genes dipped markedly several thousand years after the advent of agriculture, reported Pacific Standard.
"It wasn't like there was a mass death of males,” said Melissa Wilson Sayres, an Arizona State biologist who analyzed the DNA evidence. “They were there, so what were they doing?"
The study, published last week in the journal Genome Research, doesn’t show a reason for the drop-off in male reproduction, but the researchers tested several hypotheses.
They discounted the possibility of a “weird virus” that might have affected the world’s men.
A biological anthropologist speculated that a few men who accumulated much wealth and power attracted the most mates and passed along their advantages to their sons – perpetuating the pattern of reproductive success.
The numbers of men reproducing in comparison to women eventually fell back into line with historical norms, suggesting that “more and more people started being successful,” Sayres said.