Proc. Natl Acad. Sci. USA 105, 10693–10698 (2008)

Agriculture began in a region of the Middle East known as the Fertile Crescent. That it diffused across Europe as human populations did is broadly accepted. But how it moved into southern Africa has been little studied.

Brenna Henn of Stanford University, California, and her colleagues examined the frequency of two alternative versions of part of the Y-chromosome in 13 African populations. They also compared 10 short, repeating DNA sequences known as 'microsatellites', which vary in number across populations.

The analysis shows that early farmers in what is now Tanzania bred with local populations in south-central Africa. This suggests that pastoralism and some types of cultivation were spread across the continent by people who practised them, rather than by word of mouth — and debunks the idea that farming reached southern Africa from the west.