Neanderthal genome suggests new, mysterious human lineage (+video)

A genome sequenced from the toe bone of a Neanderthal woman has yielded several new insights into the evolution of early humans and their contemporaries.

The existence of a mysterious ancient human lineage and the genetic changes that separate modern humans from their closest extinct relatives are among the many secrets now revealed in the first high-quality genome sequence from a Neanderthal woman, researchers say.

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TheNeanderthal womanwhose toe bone was sequenced also reveals inbreeding may have been common among her recent ancestors, as her parents were closely related, possibly half-siblings or another near relation.

Although modern humans are the world's only surviving human lineage, others also once lived on Earth. These includedNeanderthals, the closest extinct relatives of modern humans, and the relatively newfoundDenisovans, whosegenetic footprintapparently extended from Siberia to the Pacific islands of Oceania. Both Neanderthals and Denisovans descended from a group that diverged from the ancestors of all modern humans. [See Photos of Neanderthal Bone & Denisovan Fossils]

The first signs of Denisovans came from a finger bone and a molar tooth discovered in Denisova Cave in southern Siberia in 2008. To learn more about Denisovans, scientists examined a woman's toe bone, which was unearthed in the cave in 2010 and showed physical features resembling those of both Neanderthals and modern humans. The fossil is thought to be about 50,000 years old, and slightly older than previously analyzed Denisovan fossils.

Human interbreeding

The scientists focused mostly on the fossil'snuclear DNA, the genetic material from the chromosomes in the nucleus of the cell that a person receives from both their mother and father. They also examined the genome of this fossil's mitochondria the powerhouses of the cell, which possess their own DNA and get passed down solely from the mother.

The investigators completely sequenced the fossil's nuclear DNA, with each position (or nucleotide) sequenced an average of 50 times. This makes the sequence's quality at least as high as that of genomes sequenced from present-day people.

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Neanderthal genome suggests new, mysterious human lineage (+video)