In the new study published today in Science, a group of European researchers sequenced five mitochondrial DNA taken from Neanderthal bones, some of which were 70,000 years old. They used a special technique to extract Neanderthal DNA from other kinds of materials that get mixed into fossils over time. What they discovered was that this DNA, taken from various regions around Europe, had many features in common.

According to Science:

[The researchers Jeffrey Good and Adrian Briggs] found 55 places out of the 16,565 bases where the mitochondrial genomes varied across the six ancient samples. On average, they found 20 differences between any two samples. In modern humans, about 60 differences exist between any two samples, making Neandertals about one-third as diverse.

Based on this lack of variation, the researchers were able to extrapolate roughly how large the population of Neanderthals might have been between 70,000 and 38,000 years ago. It appears that there were probably only about 7,000 Neandertals in Europe when homo sapiens arrived. The researchers speculate that this low population number may also have contributed to this species' eventual extinction.

The number also helps to explain other archaeological evidence, or rather the lack thereof. Scientists have found very few remains of Neanderthal cultures, and very few fossils of them as well. What this new research suggests, however, is that this tiny band spread very far across Europe. There may not have been a lot of them, they were good travelers.

Some scientists speculate that it might not be appropriate to categorize Neanderthals as a separate species at all. One might view them as an extreme variation on homo sapiens, which evolved squat bodies and thick brows to cope with the extreme cold of the European winter. Homo sapiens, which evolved in Africa, would have looked dramatically different from their pale, squat Neanderthal cousins. For now, however, Neanderthals are classified as their own species. And now it looks as if they were always a very tiny, marginal group.

via Science and Science News

Though we can't be sure what their everyday interactions were like, scientists now have one more piece of evidence that homo sapiens and Neanderthals weren't mixing their DNA.

A group of Italian researchers published a new study today in PLoS One comparing the DNA from early human bones from about 28,000 years ago with DNA Neanderthal bones. What's cool about the new study is that the early human bones are quite recently discovered, and therefore very unlikely to have been contaminated by DNA from humans who have handled them.

The researchers sequenced DNA from these bones, testing to see if there was significant overlap with Neanderthal DNA, which would indicate that homo sapiens' DNA had been changed by interbreeding with Neanderthals. Many anthropologists have long believed that the two species interbred because there are a few ancient skulls whose morphology seems to be a perfect blend of human and Neanderthal.

But tests of the fossilized DNA revealed no matches. The early human DNA from the Italian researchers' sample looked very much like modern DNA, not like Neanderthal DNA. So it looks like humans weren't getting busy with Neanderthals after all. Or if they were, they didn't have a lot of babies.

28,000 Year Old Cro Magnon Sequence [PLoS One]

A new research paper released today in PLoS Genetics says both studies may have gotten it wrong. They suggest that contamination might have screwed up Green's study, making it appear that there was a lot more admixture between the two hominids than there actually was. On the other hand, evidence from other studies make it seem likely that there was at least some mixing between human and Neanderthal, and that we have inherited some traits from those hairy, European hominids with the big foreheads who died out about 40 thousand years ago. You should expect to see more controversy coming out of Neanderthal DNA sequencing projects in coming months. People never cease to be fascinated by the idea that at one time there were two hominid populations living side-by-side in Europe — and that fascination fuels research grants. Image by Frank Franklin II for AP.

Inconsistencies in Neanderthal Genomic DNA Sequences [PLoS Genetics]