Our newest relatives hailed from around this cave in Siberia.

In 2008, scientists found a fossil of a humanoid finger in the Denisova Cave in Siberia. The finger was probably from someone (or something) that had been running around Siberia forty thousand years ago.

Until recently, the scientists would have been stuck until they found additional fossils to build up a more complete skeleton. Once they had the skeleton, they could then compare it to other fossils and figure out how it related to modern humans. Of course this might never happen—it would be totally dependent on finding more fossils.

Rather than waiting around, these scientists decided to bring in a geneticist. Nowadays geneticists can sometimes read every base of a fossilized beast’s DNA. In other words, they can read its whole genome.

When geneticists did this, they found that the finger did not come from a modern human or a Neanderthal. This Denisovan (as scientists named it) probably came from a previously unknown relative that was more closely related to Neanderthals than humans. And surprisingly, their legacy lives on in some modern humans.

By comparing the DNA of the Denisovan and various modern ethnic groups, scientists could see Denisovan DNA in modern Melanesians. Apparently the ancestors of Melanesians and Denisovans had babies before the Denisovans went extinct.

The data suggest that Denisovans might have contributed up to 4-5% of their DNA to modern Melanesians. Add the 1-2% Neanderthal DNA found in non-Africans and you get up to 7% of Melanesian DNA coming from nonhuman sources. And that is just based on the two extinct species whose DNA we’ve been able to read so far.

Who knows how much DNA of other ethnic groups comes from relatives whose DNA we haven’t looked at yet. I bet someone is taking a good hard look at various groups’ DNA to see if they can answer this question without having to figure out more fossil DNA.

This all points to an exciting new twist to paleontology…the ability to look at DNA from fossils and to compare that DNA to modern humans and any other close relatives whose DNA has been sequenced. This new avenue of research should provide extra information that scientists didn’t have before and allow them to figure some things out with just a single finger bone.

BBC story on the find.

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We are all Africans in our DNA.

We all originally came from Africa. At least that is what a couple of new studies have claimed.

Now this isn't breaking news. Other studies have looked at people's DNA and proposed the "Out of Africa" hypothesis. What is different with these studies is how many people they looked at. And how much of their DNA.

One study looked at over 500,000 DNA differences in 438 people from 29 different populations. The other looked at over 600,000 differences in 938 people from 51 different populations. This dwarfs any other previous study.

All of this data showed that East Africans had the most diverse DNA. And that the further away a population got from East Africa, the less diverse their DNA was. So how does this show that we are all Africans at heart (or at least in our DNA)?

It has to do with the fact that DNA changes over time. Everyone’s DNA is a little different from when they were a fertilized egg because of DNA mutations.

If a change happens in the DNA of an egg or sperm cell, then it will be passed to the next generation. So the group that stays longer in one place will build up more of these changes. Their DNA will be more genetically diverse.

Imagine it is 50,000 years ago and our ancestors are all in Africa. These folks have been there for hundreds of thousands or even millions of years. Over this time, there were lots of individuals all mixing their DNA. And their DNA was changing slightly generation to generation.

Now imagine that a few people develop a bit of wanderlust. They’re tired of Africa and want to see what the Arabian Peninsula looks like. So a small group takes off and heads over there. And doesn't return.

This group, which will go on to found Asia's population, is not nearly so diverse as the group they left behind. And the smaller the founding group, the less diverse their DNA will be.

Now 50,000 years later, here we are. East Africans have continued to mix and change from their big diverse starting population. Asians have mixed and changed too but from a smaller, less diverse starting population. So the East Africans are more genetically diverse than the Asians.

Now imagine it is 10,000 years ago. A small group of Asians heads over to Alaska and doesn’t return. This starting group is even less diverse than the original group of East Africans. Which helps explain why Native Americans are genetically less diverse than Asians.

The studies were so big that they were able to make even finer distinctions (see the tree to the right). And as data continues to pour in (especially from companies like 23andMe and DeCODEme),
scientists will be able to refine ancestry even further.

Dr. Barry Starr is a Geneticist-in-Residence at The Tech Museum of Innovation in San Jose, CA.

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