Malaria is an ancient and persistent disease. It wasn’t eradicated in the United States until the 1950s, and it is still devastating in developing countries around the world. The latest estimate from the World Health Organization is that in 2008 the disease killed more than a million people and afflicted 247 million others.
Scientists have long speculated about just how ancient the disease is, and when the human malaria parasite originated, with wildly varying estimates from 10,000 years to several million years ago.
Now, using statistical modeling and DNA analysis, a group of researchers report in the journal Science that ancestors of humans first acquired the malaria parasite known as P. falciparum 2.5 million years ago. But, the researchers wrote, the parasite probably did not cause disease in humans until much more recently, perhaps 10,000 years ago at the beginning of agriculture.
The researchers linked the rate of evolution in the parasites to the rate of evolution in bird hosts in the West Indies. They were able to estimate the rate at which malaria parasites would have had to diversify in order to spread to other hosts, like mammals.
As for the public health benefits of the malaria dating, there may not be too many. “Knowing how old the human malaria is isn’t going to do much in the way of curing it,” said Robert E. Ricklefs, a biologist at the University of Missouri at St. Louis and the study’s lead author.
http://www.nytimes.com/2010/07/20/science/20obmalaria.html?_r=1
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