BRONZE-AGE men in Japan had lower sperm counts than the race of people who
succeeded them, according to researchers from Japan鈥檚 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. 鈥淭hey must have
had had some other advantages,鈥� says Nakabori.
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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
(快猫短视频, 11 May 1996, p 10).