Swahili Origins

The Swahili people of coastal east Africa practiced a blend of cultural practices from around the Indian Ocean. They were Muslims and had been for a long time, perhaps the first in sub-Saharan Africa. Their trading companies were organized along lines known from pre-modern Persia, and their sailing ships were modeled on those used in the Persian Gulf and Arabian Sea. But their architecture and food were distinctly African. Their language was rooted in Bantu but had a simplified grammar and numerous words from Persian, Arabic, and Hindi. They looked African. (Above, portrait of the 19th-century Zanzibar trader known to the British as Tippu Tib.)

Old Zanzibar

Their own origin story, related to Protuguese historians in the 1500s, was that they were descended from Persian princes who sailed across the sea and married local princesses. One version comes from the Kilwa Chronicle, which purports to relate the history of the island city of Kilwa. The Chronicle tells us that a Persian king, after a disturbing dream, decided to emigrate, so he took his six sons in seven ships and sailed for Africa, buying the island from its African sovereign by laying down enough colored cloth to surround the whole island.

This basic story has, to a remarkable degree, been confirmed by a new DNA study.

Here we report ancient DNA data for 80 individuals from 6 medieval and early modern (AD 1250–1800) coastal towns and an inland town after AD 1650. More than half of the DNA of many of the individuals from coastal towns originates from primarily female ancestors from Africa, with a large proportion—and occasionally more than half—of the DNA coming from Asian ancestors. The Asian ancestry includes components associated with Persia and India, with 80–90% of the Asian DNA originating from Persian men. Peoples of African and Asian origins began to mix by about AD 1000, coinciding with the large-scale adoption of Islam.

Modern techniques allow us to speculate on how long ago various genes entered a population, and this data again matches the known history very well. The Persian DNA is the oldest foreign component, while the later mixing involves genes from India and the Arabian peninsula. This matches what the Portuguese found in the 1500s: old stories about Persians, but strong trading ties to modern Yemen and many merchants who spoke fluent Arabic.

One of the famous doors of Stone Town on Zanzibar

For nearly half the DNA of any population to come from outsiders is unusual. Current estimates are that 30 to 40% of English genes come from Anglo-Saxon invaders, while no more than 15% of Turkish genes come from Turks. Which makes it quite fascinating that this culture uses an African language and has so many other African traditions. There are a few likely reasons for this. First, the 80 people we know about are all probably from the elite, and the story of the common people may be different. (The authors of this study say they are looking for non-elite burials now.) Also, the migrants from Persia seem to have been overwhelmingly male, so perhaps the migrant traders left all affairs on the women's side of the house to their wives, including the raising of children.

Ruins in old Gede, a medieval Swahili town

David Reich, one of the authors of the study, has a somewhat different take. He told the NY Times that Persian culture did not dominate outside the mercantile realm because this was not a violent conquest. As the story of Kilwa suggests, the foreign traders reached accommodations with local peoples and leaders. Without supreme political power, they were absorbed by the local world rather than dominating it. 

(Which is nice, but on the other hand the main business of Swahili merchants was always trading African slaves, which went on until the British navy stamped it out in the 1840s.)

And here is another way that paleogenetics has confirmed legends that allegedly scientific archaeologists dismissed in the 1950-2000 period. For whatever reason –something to do with Nazis and the Vietnam War, so far as I can tell – local evolution came to be the gospel. Recent histories of the Swahili coast have downplayed stories of foreign arrivals and tried to derive the whole culture (except Islam) from local traditions. But the local storytellers were right, and men who sailed across the sea from Persia were a big part of their society's origin. Likewise with the Anglo-Saxons, who really did invade Britain and conquer it, and the Lombard invasion of Italy, and many other cases. The old Irish story that their island has seen at least four waves of invasion looks better and better in the light of modern genetics.

I love living in a time when so many of these old, intractable debates have actually been resolved by science.