DNA from an ancient toe bone has provided new insight into the lives of Neanderthals, revealing that inbreeding was common among the group.

Scientists sequenced DNA from a 50,000-year-old toe bone of a female Neanderthal, found in Denisova Cave in Siberia, where fossilized remnants of human ancestors were found in 2010, according to the report in the journal Nature. The analysis suggested that her parents were genetically close enough to be either half siblings, first cousins or an uncle and a niece.

The findings suggest the population of Neanderthals was small, making inbreeding more common among them than among ancestors of modern humans, said David Reich, a study author and professor of genetics at Harvard Medical School in Boston. The low levels of genetic diversity also may have made them less fit over the long run.

Neanderthals were thought to have lived in Europe until 30,000 years ago, possibly overlapping with modern humans there, according to an accompanying editorial by Ewan Birney, a biologist at the Wellcome Trust Genome Campus in Cambridge, England, and Jonathan Pritchard, a geneticist at Stanford University in California.

Front Section, Pages 5 on 12/19/2013