A long history of mercantile trade along the eastern shores
of Africa left its mark on the DNA of ancient Swahili people.
A new analysis of centuries-old bones and teeth collected
from six burial sites across coastal Kenya and Tanzania has found that, around
1,000 years ago, local African women began having children with Persian traders
— and that their descendants gained power and status in the highest levels of
pre-colonial Swahili society.
اضافة اعلان
The findings help elucidate the foundations of Swahili
civilization, and suggest that long-told origin stories, passed down through
generations of Swahili families, may be more truthful than many outsiders have
presumed.
“The genetics corroborate the Swahili people’s own history
that they tell about themselves, not what others were saying about them,” said
Esther Brielle, a geneticist and postdoctoral fellow at Harvard University who
led the DNA analysis with her adviser, David Reich.
The researchers published their findings last week in the
journal Nature.
The Swahili Coast is a narrow strip of land that stretches
some 3.218km along the Eastern African seaboard — from modern-day Mozambique,
Comoros and Madagascar in the south, to Somalia in the north. In its medieval
heyday, the region was home to hundreds of port towns, each ruled
independently, but with a common religion (Islam), language (Kiswahili) and
culture.
The genetics corroborate the Swahili people’s own history that they tell about themselves, not what others were saying about them.”
Many towns grew immensely wealthy thanks to a vibrant
trading network with merchants who sailed across the Indian Ocean on the
monsoon winds. Middle Eastern pottery, Asian cloths and other luxury goods came
in. African gold, ivory and timber went out — along with a steady flow of
enslaved people, who were shipped off and sold across the Arabian Peninsula and
Persian Gulf. (Slave trading later took place between the Swahili coast and
Europe as well.)
A unique cosmopolitan society emerged that blended African
customs and beliefs with those of the foreign traders, some of whom stuck
around and assimilated.
Islam, for example, arrived from the Middle East and became
an integral part of the Swahili social fabric, but with coral-stone mosques
built and decorated in a local, East African style. Or consider the Kiswahili
language, which is Bantu in origin but borrows heavily from Indian and Middle
Eastern tongues.
The arrival of Europeans, beginning around 1500, followed by
Omani sailors some 200 years later, changed the character of the region. Yet,
aspects of the heritage and traditions that took root in the Middle Ages remain
evident in East Africa today.
Researchers who have studied the region have long debated
where those influences came from.
At first, most scholars thought that the civilization, with
its lavish mosques and ornate housewares, must have been the achievement of a
foreign ruling class that established outposts in East Africa. But over the
past 40 years, archaeologists, linguists and historians have come to see
Swahili society as predominantly homegrown — with outside elements adopted over
time that had only a marginal impact.
That African-centric version of Swahili roots never sat well
with the Swahili people themselves, though.
They generally preferred their own origin story, one in which
princes from present-day Iran (then known as Persia) sailed across the Indian
Ocean, married local women and enmeshed themselves into East African society.
Depending on the narrative source, that story dates to around 850 or 1000 — the
same period during which genetic mixing was underway, according to the DNA
analysis.
“It’s remarkably spot on,” said Mark Horton, an
archaeologist at the Royal Agricultural University of England who has worked on
the Swahili coast for decades.
“This oral tradition was always maligned,” added George
Abungu, an archaeologist and former director-general of the National Museums of
Kenya (who, like Horton, was not involved in the genetic analysis). “Now, with
this DNA study, we see there was some truth to it.”
The ancient DNA study is the largest of its kind from
Africa, involving 135 skeletons dating to late-medieval and early-modern times,
80 of which have yielded analyzable DNA.
To figure out where these people came from, the researchers
compared genetic signatures from the dug-up bones with cheek swabs or saliva
samples taken from modern-day individuals living in Africa, the Middle East and
around the world.
The burial-site DNA traced back to two primary sources:
Africans and present-day Iranians. Smaller contributions came from South Asians
and Arabs, with foreign DNA representing about half of the skeletons’
genealogy.
“It’s surprising that the genetic signature is so strong,”
said Jeffrey Fleisher, an archaeologist at Rice University who helped excavate
the Tanzanian sites included in the analysis. He had predicted that the genetic
influence from outside of Africa would be much smaller, he said.
Different patterns of inheritance for different stretches of
DNA have revealed how the genetic mixing came about.
“It’s surprising that the genetic signature is so strong.”
Gene sequences from tiny power factories inside the cell,
known as mitochondria, were overwhelmingly African in origin. Since children
inherit these bits of DNA only from their mothers, the researchers inferred
that the maternal forebears of the Swahili people were mostly of African
descent.
By comparison, the Y chromosome, passed from father to son,
was chock-full of Asian DNA that the researchers found was common in modern-day
Iran. So, a large fraction of Swahili ancestry presumably came from Persian
men.
The picture that emerges is one of Persian men mixing with
African women at multiple locations along the Swahili Coast around the turn of
the first millennium, with each group contributing about half of the genes that
are found in Swahili people today. (African men and Indian women added small
amounts to the gene pool.)
“The genetic evidence enriches our understanding of the
history,” said Abdul Sheriff, a historian and former museum curator in
Zanzibar, Tanzania. “All of this really jells together to explain more fully
how this civilization came about.”
Reich initially assumed that conquering men settled the
region by force, displacing the local males in the process. “My hypothesis was
that this was a genetic signature of inequality and exploitation,” he said.
This is what he had seen in other parts of the world. In the
Americas, for example, where a history of colonization, enslavement and
subjugation explains why almost all the foreign ancestry in African American
and Latin American individuals comes from European males.
But that turned out to be a “naive expectation,” Reich said,
because “it didn’t take into account the cultural context in this particular
case.”
In East Africa, Persian customs never came to dominate.
Instead, most foreign influences — language, architecture, fashion, arts — were
incorporated into a way of life that remained predominantly African in
character, with social strictures, kinship systems and agricultural practices
that reflected Indigenous traditions.
“Swahili was an absorbing society,” said Adria LaViolette,
an archaeologist at the University of Virginia who has worked on the East
African coast for more than 35 years. Even as the Persians influenced the
culture, “they became Swahili,” she said.
One major caveat to the study: Nearly all the bones and
teeth came from ornamental tombs that were located near grand mosques, sites
where only the upper class would have been laid to rest. As such, Chapurukha
Kusimba, one of the study’s authors, said that the results might not be
representative of the general populace.
A Kenyan-born anthropological archaeologist from the
University of South Florida, Kusimba is now looking for skeletons from less
well-to-do burial sites along the Swahili coast. But until he has those gene
sequences in hand, it will be impossible to say just how far-reaching the
foreign influence has been on the DNA of people of Swahili descent.
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