A computer-generated image of a single Neanderthal toe bone found in a Siberian cave in 2010.
Bence Viola

“We thought it would be a Denisovan toe,” said Dr. Paabo, “but it very clearly was a Neanderthal.”

The scientists were able to reconstruct the new Neanderthal genome even more accurately than the Denisovan one.

The crisp focus of the new genome is yielding new discoveries about Neanderthals. For example, Dr. Paabo and his colleagues can distinguish the origin of each piece of DNA — whether it came from the Neanderthal’s mother or father. With an X chromosome from each parent, the toe belonged to a female.

A closer look at these two sets of DNA revealed that the Neanderthal female was extremely inbred. Her two parental sets of genes were identical for long stretches. Such similarity can only come about when close relatives have children.

“We don’t know if this is typical of all Neanderthals, or just this population in Siberia,” said Dr. Paabo. It will take more high-caliber Neanderthal genomes to settle that question.

The new genome reveals not just inbreeding but interbreeding. The accompanying diagram summarizes the flow of DNA between human lineages over the past half million years, based on a comparison of the new Neanderthal genome with other Neanderthal DNA sequences, the Denisovan genome and the genomes of living humans.


A new study of ancient DNA indicates that modern humans branched off from ancestors of Neanderthals and Denisovans around 600,000 years ago. Later, interbreeding moved DNA between the branches. The percentages show how much DNA in a genome arrived through interbreeding. For example, people in Oceana have 3 to 6 percent Denisovan DNA.
Nature
A new study of ancient DNA indicates that modern humans branched off from ancestors of Neanderthals and Denisovans around 600,000 years ago. Later, interbreeding moved DNA between the branches. The percentages show how much DNA in a genome arrived through interbreeding. For example, people in Oceana have 3 to 6 percent Denisovan DNA.

Dr. Paabo and his colleagues were able to detect not one, but two injections of Denisovan DNA into the modern human gene pool.

Intriguingly, the Denisovan genome also contains hints of even more exotic interbreeding. A few percent of their DNA appears to have originated from a more distant branch of our evolutionary tree.

Dr. Paabo said it was possible that the branch was a species known as Homo erectus, which lived across much of the Old World from 1.8 million to about 50,000 years ago.

Dr. Tishkoff thinks this is a possible explanation of the data, but not the only one. She thinks it is possible that the same pattern could have emerged if the ancestors of humans, Neanderthals and Denisovans in Africa became separated from each other early on, evolving different DNA sequences.

Despite all the flowing DNA, Neanderthals, Denisovans and modern humans did not become one big genetic blur. After Denisovan and Neanderthal DNA made its way into the modern human gene pool, most of it gradually disappeared. And modern humans took their own evolutionary path.

By comparing their high-quality ancient genomes to human genomes, Dr. Paabo and his colleagues are drawing up a list of mutations that are unique to our own lineage. “I would say it is a definitive list,” said Dr. Paabo.

Dr. Paabo is intrigued by some mutations that affect genes involved in the development of the brain. But he sees the list as only a starting point for research.

“What lies ahead is to understand which of these is important,” said Dr. Paabo. “That’s totally up in the air.”


For more Information on the Human Ancestry go to:

Wikipedia - Homo

Wikipedia - Homo Sapiens

Wikipedia - Anatomically Modern Humans (homo sapien sapiens)

Wikipedia - Human


Map of the migration of modern humans out of Africa, based on mitochondrial DNA:
Coloured rings indicate years before present, in thousands

Summary

World map of human migrations, with the North Pole at center. Africa, harboring the start of the migration, is at the top left and South America at the far right. Migration patterns are based on studies of mitochondrial (matrilinear) DNA. Dashed lines are hypothetical migrations.

Numbers represent thousand years before present.

The blue line represents area covered in ice or tundra during the last great ice age.

The letters are the mitochondrial DNA haplogroups (pure motherly lineages); Haplogroups can be used to define genetic populations and are often geographically oriented. For example, the following are common divisions for mtDNA haplogroups:
  • African: L, L1, L2, L3
  • Near Eastern: J, N
  • Southern European: J, K
  • General European: H, V
  • Northern European: T, U, X
  • Asian: A, B, C, D, E, F, G (note: M is composed of C, D, E, and G)
  • Native American: A, B, C, D, and sometimes X
Data derivation