Planet Earth Online

Caribbean slaves came from different regions in Africa

13 August 2009, by Sara Coelho

'We knew from historical records that the plantation was worked by African slaves,' says archaeologist Dr Hannes Schroeder who led the research while working for his PhD at the University of Oxford. 'But now we have a method that enables us to identify first-generation captives among the burials and to trace their origins back to their native Africa.'

Previous research at Newton mainly focused on the slaves' nutrition and physical quality of life. But their origin was still a mystery - how many of them had been born in Africa as opposed to Barbados? And where in Africa had they come from?

Schroeder and his team collected bone and tooth samples from the skeletons of 25 individuals, hoping to find clues in their isotopic composition. Not every atom of an element is the same: some are heavier than others and the proportion between different atom types, or isotopes, gives information about diet and environmental conditions.

'Isotope analyses provide a reliable way to identify migrants in archaeological populations,' says Schroeder. The team analysed several types of isotopes: carbon and nitrogen isotopes which give clues about diet, oxygen isotopes which are sensitive to environmental conditions and radiogenic strontium isotopes which reflect the underlying rocks.

They found that the teeth of seven individuals had distinct carbon and nitrogen isotope signatures, lower than the average. But the bones of these individuals held higher carbon and nitrogen isotope ratios, similar to the rest of the group.

Schroeder explains: 'Bone tissue remodels throughout life whereas teeth remain the same after they are formed. If the isotopic ratios vary between the bones and teeth of a single individual , then this suggests a major change in diet and possibly residence at some point during life.'

For the seven individuals from Newton, the change occurred when they were abducted from their native Africa and transported to a life of slavery in the Caribbean. The strontium isotope analysis strengthened the conclusion.

Barbados is capped with limestone, a marine rock which bears the same strontium isotope signature as the ocean. 'This is why people native to Barbados have roughly the same strontium isotope ratio as seawater,' says Schroeder. 'But the seven individuals from Newton had higher strontium isotope values, which suggest that they grew up in a continental area with old rock formations.' Africa fits the bill.

Schroeder is confident that isotopes provide the scientific backing needed to identify African-born individuals in the New World. But the results, published last week in the American Journal of Physical Anthropology, also show that the slaves did not all come from the same region in Africa. Three of the seven African-born individuals were raised on a diet rich in crops adapted to hot conditions, such as sorghum and millet, while the other four grew up eating crops like rice and yams during their childhood. 'This suggests that the slaves might have came from different areas in Africa, as widely apart as the Senegambia, where people to this days still subsist largely on rice agriculture, and the Gold Coast, for example,' says Schroeder.

The method, however, has its shortcomings: 'isotopes can tell where someone was born, but they don't reveal anything about ancestry.' Schroeder, who now works at the Centre for Ancient Genetics of the University of Copenhagen in Denmark, now focuses his research on genetic markers such as mitochondrial DNA to fill this gap.

Keywords: Africa, Biodiversity,

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