The most widespread form of human malaria originated in Africa - not Asia as was previously thought, research suggests.
A study of malaria parasites from African primates has enabled researchers to unravel the evolutionary origins of the disease.
Their findings could have important implications for efforts to eradicate malaria from human populations.
The study explains why almost all natives of central Africa have a genetic mutation that makes them resistant to this type of malaria, even though there had seemed to be no risk of infection in the region.
Researchers studied the DNA of malaria parasites in thousands of faecal samples from wild apes across central Africa.
They found a type of malaria parasite that is widespread among chimpanzees and gorillas in the area.
It is genetically almost identical to one that affects many millions of people each year across the tropics, apart from in central Africa.
The findings suggest that the parasite, known as Plasmodium vivax, originally affected gorillas, chimps and people in Africa.
However, thousands of years ago, people in the region developed a genetic mutation that prevents infection, which spread in central Africa and is still prevalent.
Until now, the closest relatives of this parasite had only been found in Asian primates, leading to the belief that the disease had originated there.
Our new understanding of the origins of this malaria parasite has solved a number of mysteries, and has important implications as efforts to eradicate malaria are intensified.