Thursday, August 21, 2014

Seals, tuberculosis, and DNA

Article: Seals carried tuberculosis across the Atlantic, gave it to humans: Disease was present in the Americas prior to European contact.
This offers a glimpse at the rather complicated history of tuberculosis.

TB leaves recognizable changes in bones. Therefore, it can be the diagnosed from skeletons of the long dead.

In the Old World, the bacteria causing TB made the leap to humans about 10,000 years ago. After that, it made the leap from humans to cattle.

It is known that Native Americans had TB early on. This gave rise to the belief that Westerners brought it to the Americas. However, pre-Columbian skeletons were found showing the disease.

So, if the land bridge from Asia was submerged more than 10,000 years ago, how did the disease get here?

Turns out that bacterial DNA from three, 4,000 year old skeletons of Native Americans in Peru was not the normal, human variant. It was the "pinniped" variation. That is, seals carried TB from Africa to South America, and from there across the Americas.

Seals also carried TB to Australian Aborigines about 700 year ago.

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