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Humans carried Plasmodium falciparum with them out of Africa

Sun, 20th Jun 2010

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This week, a team of scientists have shown that one of the deadliest strains of malaria travelled with early humans as they left Africa and colonised Asia.
The current understanding is that modern humans evolved in the Afar region of Ethiopia. About 55 thousand years ago, they began to migrate out of Africa to colonise what is now Europe and Asia.

Plasmodium falciparumThe paper, published in Current Biology, describes that there is a decline in the genetic diversity of the populations of Plasmodium falciparum as you move further away from sub-Saharan Africa. The team collected blood from individuals infected with falciparum from countries in Africa to South East Asia and South America. Because Plasmodium falciparum only infects humans, it can only have been transported out of Africa via humans. The team compared the genetic diversity of the parasite with the timing of migrations out of Africa.

It’s already well documented that the genetic diversity of human populations decreases as you move further away from sub-Saharan Africa, because people have simply been there for less time and there has been less time for new mutations to arise. The team found that the genetic diversity of the parasite decreased with distance in exactly the same way, and the age estimates fitted with the parasite accompanying the migrating early humans, with the exception of South America, where the results pointed to a much more recent invasion of the parasite – probably to do with the slave trade.

The genetic diversity of the malaria parasite plays a key role in how dangerous it is, so knowing more about the diversity can help us to find better ways to fight it, which given that falciparum is the most dangerous strain of malaria, is a very good thing.



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