Shared genes with Neanderthal relatives not unusual
1 November 2011
During human evolution our ancestors mated with Neanderthals, but also with other related hominids. In this week’s Net edition of PNAS researchers from Uppsala University are publishing findings that show that people in East Asia share genetic material with Denisova man, which received its name from the cave in Siberia where it was first found.
- Our studies cover a larger part of the world than earlier studies, and it’s perfectly clear that it’s not as simple as we previously thought. Instead, hybridization took place at several points in evolution, and the genetic traces of this are found in several places in the world. We’ll probably be uncovering more events like these, says Mattias Jakobsson, who performed the study together with Pontus Skoglund.
Previous studies have found two separate hybridization events between so-called archaic humans (different from modern humans in both genetics and morphology) and the ancestors of today’s humans after modern humans spread outside of Africa: hybridization between Neanderthals and the precursors of modern humans outside of Africa and hybridization between Denisova man and the ancestors of the aboriginal people of Oceania. The genetic difference between Neanderthals and Denisova man is roughly as great as the maximal variation among us modern humans.
The Uppsala scientists’ study confirms that hybridization also occurred on the East Asian mainland. The connection was discovered by using so-called genotype data in order to obtain a larger data material. The complete genetic make-up for modern humans is only available from some dozen individuals today, whereas genotype data is available from thousands of people. These can be compared with genome sequences from Neanderthals and Denisova man, which have been determined from archeological material. Only a little finger and a tooth have been described from the latter.
Genotype data comes from genetic research where hundreds of thousands of genetic variants from test panels are gathered on a chip. However, this process entails that unusual variants disappear, which can lead to aberrations if the material is treated as if it consisted of complete sets. Skoglund and Jakobsson have used advanced computer simulations to calculate 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 above all 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 flows from archaic human groups also occurred on the Asian mainland, says Mattias Jakobsson.
- We can see that the genetic heritage from archaic human groups lives on to a greater extent than was previously thought, but 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 judge that hybridization with Denisova man ought to have taken place about 20,000–40,000 years ago. This is long after the branch that became modern humans split off from the branch that became so-called archaic humans some 300,000-500,000 years ago.
- With more complete gene sets from modern humans and more analyses of fossil material, it will be possible to relate our prehistory with considerably greater certainty and richer detail, says Mattias Jakobsson.
For more information, please contact Mattias Jakobsson, phone: +46 (0)18-471 64 49; mobile: +46 (0)73-698169, firstname.lastname@example.org or Pontus Skoglund, phone: +46 (0)18-471 28 93; mobile: +46 (0)76-8393733, email@example.com