Shared genes with Neanderthal relatives not unusual

Oct 31, 2011

During human evolution our ancestors mated with Neanderthals, but also with other related hominids. In this week's online edition of PNAS (Proceedings of the National Academy of Sciences), researchers from Uppsala University are publishing findings showing that people in East Asia share genetic material with Denisovans, who got the name from the cave in Siberia where they were first found.

Our study covers a larger part of the world than earlier studies, and it is clear that it is not as simple as we previously thought. Hybridization took place at several points in evolution, and the genetic traces of this can be found in several places in the world. We'll probably be uncovering more events like these, says Mattias Jakobsson, who conducted the study together with Pontus Skoglund.

Previous studies have found two separate hybridization events between so-called archaic humans (different from in both genetics and morphology) and the ancestors of modern humans after their emergence from Africa: hybridization between and the ancestors of modern humans outside of Africa and hybridization between Denisovans and the ancestors of indigenous Oceanians. The between and Denisovans is roughly as great as the maximal level of variation among us modern humans.

The Uppsala scientists' study demonstrates that hybridization also occurred on the East Asian mainland. The connection was discovered by using genotype data in order to obtain a larger data set. Complete genomes of modern humans are only available from some dozen individuals today, whereas genotype data is available from thousands of individuals. These can be compared with genome sequences from Neandertals and a Denisovan which have been determined from archeological material. Only a pinky finger and a tooth have been described from the latter.

Genotype data stems from genetic research where hundreds of thousands of genetic variants from test panels are gathered on a chip. However, this process leads to unusual variants not being included, which can lead to biases if the material is treated as if it consisted of complete genomes. Skoglund and Jakobsson used advanced computer simulations to determine what this source of error means for comparisons with archaic genes and have thereby been able to use genetic data from more than 1,500 modern humans from all over the world.

We found that individuals from mainly Southeast Asia have a higher proportion of Denisova-related genetic variants than people from other parts of the world, such as Europe, America, West and Central Asia, and Africa. The findings show that gene flow from archaic human groups also occurred on the Asian mainland, says Mattias Jakobsson.

While we can see that genetic material of archaic humans lives on to a greater extent than what was previously thought, we still know very little about the history of these groups and when their contacts with modern humans occurred, says Pontus Skoglund.

Because they find Denisova-related gene variants in Southeast Asia and Oceania, but not in Europe and America, the researchers suggest that hybridization with Denisova man took place about 20,000,000 years ago, but could also have occurred earlier. This is long after the branch that became modern humans split off from the branch that led to Neandertals and Denisovans some 300,000-500,000 years ago.

With more complete genomes from modern humans and more analyses of fossil material, it will be possible to describe our prehistory with considerably greater accuracy and richer detail, says Mattias Jakobsson.

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User comments : 8

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barefoot
5 / 5 (1) Nov 01, 2011
Shouldn't it read 20 thousand years ago in the article rather than 20 million?
Pirouette
3 / 5 (2) Nov 01, 2011
no, 20 million is correct. Mankind has been in existence for much more than only 20 thousand years.
Nerdyguy
not rated yet Nov 01, 2011
Confusion appears to derive from the wording in the article.

"This is long after the branch that became modern humans split off from the branch that led to Neandertals and Denisovans some 300,000-500,000 years ago. "

It should read "This is long before...", referring to the 20 million years.
nkalanaga
5 / 5 (1) Nov 01, 2011
It's 20,000. Humans as a species haven't been around 20,000,000 years. Primates have been, but not humans.
Nerdyguy
not rated yet Nov 01, 2011
It's 20,000. Humans as a species haven't been around 20,000,000 years. Primates have been, but not humans.


You didn't read the article. It does not say what you have attributed to it.

From the article:
"researchers suggest that hybridization with Denisova man took place about 20,000,000 years ago, but could also have occurred earlier."
barefoot
5 / 5 (1) Nov 01, 2011
Looks like this article has it wrong. Found the paper on pnas.org and it says:
"The lack of evidence of Denisova ancestry in other Eurasian
populations indicates that this genetic material was introduced
into the ancestral population of Southeast Asians after the time of divergence from Europeans, a date that has been estimated to 23-45 kya but could also have occurred considerably earlier."

So thousands of years ago, not millions.
Ethelred
5 / 5 (2) Nov 01, 2011
no, 20 million is correct. Mankind has been in existence for much more than only 20 thousand years.
Mankind has NOT been in existence for 20MY. Not even sure the earliest apes showed up that long ago.

You didn't read the article. It does not say what you have attributed to it.

From the article:
"researchers suggest that hybridization with Denisova man took place about 20,000,000 years ago, but could also have occurred earlier."
I read the article. The article is WRONG. Humans haven't been around for 20MY.

It was simply mis-written in the article. Nothing new about that. A lot articles on physorg have numerical errors of three orders of magnitude. There is a lack of editing. Kind of like my own posts. I leave out a lot of words sometimes. It is very hard to see your own errors.

Ethelred
DavidMcC
not rated yet Nov 02, 2011
"While we can see that genetic material of archaic humans lives on to a greater extent than what was previously thought..."

I wonder how reliable a genetic clock you get from actual genes. A proper "genetic clock" avoids gene coding sequences like the plague, because of selection, which is usually selection for being the same, leading to gross under-estimation of dates of separation.

Unfortunately, the article isn't clear about what it means by "genetic material".