The conquest of the few

2019-03-07 04:14:01

By Peter Hadfield in Tokyo BRONZE-AGE men in Japan had lower sperm counts than the race of people who succeeded them, according to researchers from Japan’s Tokushima University. Yutaka Nakabori and his colleagues took sperm samples from 198 men and categorised them into Jomon-type and Yayoi-type, based on their genetic similarity to the two races of ancient Japanese people. The Jomon, who inhabited the Japanese islands from around 10 000 BC, have a different Y chromosome pattern to the Yayoi, who migrated from China and Korea after 300 BC. The modern descendants of the Jomon had a 20 per cent lower sperm count that the Yayoi, the team reports in the September issue of the Journal of Human Genetics (vol 44, p 240). But how the Jomon managed to survive and pass on their genes despite being outgunned by the Yayoi is not clear. “They must have had had some other advantages,” says Nakabori. The results show genetic differences are important in studies of sperm counts, says Nakabori. Geographical variations have already cast doubts on studies suggesting a worldwide decline in sperm counts (New Scientist, 11 May 1996,