A mutated gene which may protect malaria patients from the worst effects of the disease could help scientists in their hunt for a vaccine.
Malaria is transmitted by mosquitoes
The change in the CR1 gene, say Edinburgh University experts, may have evolved as a defence against malaria.
It seems to stop red blood cells "sticking" together and blocking blood vessels when malaria infection strikes.
In Papua New Guinea, which has high rates of malaria, up to 80% of the population carry the gene mutation.
This suggests that it gives a distinct evolutionary advantage in countries where malaria is rife.
The normal version of CR1 produces a "sticky" protein on the surface of the red blood cell, which links to a protein produced by the malaria parasite.
This leads, in the most severe cases of malaria, to an effect where uninfected red blood cells form a cluster around infected cells.
This can cause blockages in blood vessels supplying major organs, perhaps leading to organ failure.
This "rosetting" of blood cells is a phenomenon only spotted in the most severe malaria cases, and the Edinburgh scientists believed that some people's genetic makeup might render them more vulnerable to the effect.
In countries where malaria is uncommon, the CR1 mutation - which leads to a lack of the "sticky" proteins on the cell surface - is also rare.
The latest research, published in the Proceedings of the National Academy of Sciences, focused on people in Papua New Guinea in the Pacific Ocean, an island where malaria remains commonplace.
They found, through genetic testing, that the mutated form of CR1 was very common - four out of five people they tested had it.
This points strongly to CR1 - and its role in blood rosetting - being a key factor in whether or not a patient survives a malaria infection.
Over centuries, those with the mutated gene were more likely to survive long enough to have children, meaning that, through evolution, the proportion of people in the population carrying it gradually rose.
This is how evolution works - genes can be "selected" depending on the degree of natural advantage they give the carrier. The bigger the advantage - as in this case - the stronger the "selection" effect.
Having now identified CR1 as probably important in the body's response to malaria, the research team believes that it could offer clues to an effective vaccine.
Dr Alexandra Rowe, one of the researchers involved in the project, told BBC News Online it might be possible to create a vaccine that targeted the protein on the surface of the malaria parasite that allowed it to form a link with the CR1 blood cell protein.
She said: "It might be possible to create a vaccine this way - although there is a high degree of variation in the appearance of this protein in different malaria parasites."