New York, Dec 17 (IANS): Using DNA extracted from the remains of extinct giant lemurs, researchers may have discovered why Madagascar's largest lemurs disappeared.

Most scientists agree that humans played a role in the giant lemurs' extinction by hunting them for food and forcing them out of habitats.

"But ancient DNA extracted from the bones and teeth of giant lemurs suggests that the largest lemurs were more prone to extinction than smaller-bodied species because of their smaller population sizes," said researchers from University of Antananarivo in Madagascar and Duke Lemur Centre at Duke University in North Carolina.

Using genetic material extracted from lemur bones and teeth dating back 550 to 5,600 years, the team analysed DNA from as many as 23 individuals from each of five extinct lemur species that died out after human arrival.

The study also included genetic data from eight extant species, including the three largest lemur species still alive today.

The researchers found that the species that died out had lower genetic diversity than the ones that survived - a hallmark of small population size.

"Larger-bodied species often need larger territories and are fewer in number than smaller-bodied species. So they would have been more susceptible to extinction as hunting, logging, farming and other human activities took their toll," said George Perry, scientist from Penn State University, who was part of the research team.

The researchers hope that lessons learned from ancient DNA will be useful in protecting the species that remain.

More than 70 percent of the roughly 100 lemur species living today are now considered endangered or critically endangered by the International Union for the Conservation of Nature (IUCN), making them the most threatened group of mammals on the earth.

The study appeared in the Journal of Human Evolution.