Researchers from the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, have discovered that the genetic makeup of Neanderthals was less diverse than modern humans, and their populations were typically smaller while they lived in more isolated groups.

To gather data for the study, analysts sequenced the Neanderthal genome in 2010. Study author and evolutionary geneticist from the Max Planck Institute Svante Pääbo and his colleagues focused on three Neanderthal genomes; one that was from a 49,000-year-old sample from Spain, one 50,000- year-old sample from Siberia and a 44,000-year-old specimen from Croatia.

"For the first time we begin to get a detailed picture of genetic variation among Neanderthals," Pääbo told LiveScience.

The researchers discovered that the Neanderthal gene is less varied than that of a modern human's. Pääbo explained that the genetic diversity observed in Neanderthals is only 25 percent as varied as the genes of modern-day Africans and about a third of Europeans and Asians.

To understand why the genes of Neanderthals are less diverse, the researchers examined 17,367 genes responsible for producing proteins. They tried to map out mutations triggered by changes in amino acids, as these shifts are likely to cause an alteration in the structure of the protein. They found that Neanderthals have more amino acids responsible for mutations than a modern human does. This fact suggested that Neanderthals from Eurasia had a small population and were more likely to be isolated.

"Neanderthals seem to have been few in numbers either over a long time or for some periods," Pääbo said to LiveScience. "There is also an indication that they have been subdivided in populations that had little contact with each other."

Neanderthals are the closest relatives of modern humans - we share a common ancestor who lived around 550,000 to 765,000 years ago. Modern humans and Neanderthals also interbred at one point in history, giving people living in present-day Africa have a 1.5 to 2.1 percent DNA stamp of a Neanderthal.

Further details of the study were published in the April 21 issue of Proceedings of the National Academy of Sciences.