Neanderthal populations were small and isolated, according to a new study published in the Proceedings of the National Academy of Sciences (PNAS).

New DNA analysis shows that Neanderthals lived in small groups, which left them with a shallow gene pool. While examples of Neanderthals' genetic variation can be found by looking at their varying skeletons, they had relatively fewer changes in their behavior and pigmentation than other prehistoric human species, LiveScience reported.

"For the first time, we begin to get a detailed picture of genetic variation among Neanderthals," Svante Paabo, the study’s author and an evolutionary geneticist at the Max Planck Institute for Evolutionary Anthropology in Leipzig, said.

While Neanderthal DNA has been mapped before, this study compared ancient gene maps with those of modern humans. The results may help researchers identify which genes distinguish humans from their ancestors and discover the origin of certain genetic ailments.

Three Neanderthal genomes were analyzed: one from a 49,000-year-old specimen from Spain, another from a 44,000-year-old specimen from Croatia and another from a 50,000-year-old Siberian specimen. The findings showed that Neanderthals "had even less variation than present-day humans, who are already known to have less than chimpanzees and most other apes," Paabo said.

The comparison study found that modern humans have genes linked to cardiovascular health and metabolism that Neanderthals lacked. Humans also have genes for skin and hair color that Neanderthals did not.

But the study has its limits, since “humans today have a recent history of massive population growth," Paabo told National Geographic. To discover what truly differentiates Neanderthals from humans, "we need to figure out how much of today's pattern comes from ancient hunter-gatherers, and how much comes from our recent adaptation," he said.

The PNAS study is linked to an Israeli one published in Science that found that there is only a 0.12 percent difference, on average, between Neanderthal genes and those of Homo sapiens. That study illustrated how genetic differences between the two groups led to Neanderthals possessing bigger hands, shorter arms and a more muscular build.

While Neanderthal DNA shows that the human ancestors underwent many genetic changes, it doesn't necessarily mean that they were more evolved than humans.

"Clearly, Neandertals were not 'less evolved' than modern humans," Paabo said. "They had their own history and evolution. They took another path, if you like."

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