On the 7th of May 2010, the first genome of a human species other than ours has been published. The sequencing of the genome was carried out at the Max Planck Institute for Evolutionary Anthropology under the direction of Prof. Svante Pääbo. Science magazine has published a special section on its website for the achievement, including papers and interviews to paleoanthropologist Chris Stringer (Natural History Museum, London), geneticist Sarah Tishkoff (University of Pennsylvania), and project leader Svante Pääbo (Max Planck Institute for Evolutionary Anthropology). An older but still relevant interview with Prof. Svante Pääbo is also available online.
Svante Pääbo with a reconstructed Neandertal skull. (Copyright: Frank Vinken)
In my previous post in this blog I had just mentioned that the study of hominins was particularly active this year, to the point that we know now that in the recent past (since our species appeared) several other human species shared our planet and the tree of human life is becoming increasing complex. In Atapuerca a hominin different from Homo erectus may be a new species, as it has been the case for Homo floresiensis and the recent Siberian woman.
Marco de la Rasilla and Svante Pääbo at the El Sidron Cave in Asturias, Spain. (Copyright: El Sidron Research Team)
The genome is not as complete as that of a modern human due to the poor preservation of ancient DNA. This is why the researchers call the Neandertal genome a draft genome. It is however usable, especially in studies comparing Neandertals to modern humans and other primates. The most significant finding from the preliminary study has been that Neandertals were biologically compatible with modern humans (the two share 98.84% of their genome) and between 1% to 4 of their nuclear distinctive DNA can be found among some modern humans, namely non-Africans. This means that some interbreeding between anatomically modern humans and Neandertals probably occurred (unless an as yet unknown ancestor shared DNA with both), possibly as early as 80,000 years ago, when the two species first met in the Levant. The interbreeding was not widespread, but significant enough to affect the DNA of modern human populations. It is unknown what the function of the Neandertal genes passed on to modern humans might have been. Neandertals in the Levant manufactured more sophisticated tools than modern humans and seem to have been better adapted to colder weather. Studies on human evolution past the interbreeding event have also started, but nothing conclusive is available yet.
Entrance of the Vindija Cave, Croatia. (Copyright: Johannes Krause, Max Planck Institute for Evolutionary Anthropology)
The sequencing of the Neandertal genome has been challenging because of the difficulties in having to use DNA from different individuals to create a single sequence and the poor state of preservation and contamination (both biological and chemical) of the surviving DNA. Bones from six Neandertal fossils have been used, primarily from Vindija cave, Croatia and parts of the DNA have been sequenced from fossils from Neander Valley, Germany; El Sidron cave, Asturias, Spain; and Mezmaiskaya, Altai Mountains, Russia. Neandertals lived until 30,000 years ago in Europe and parts of the Levant, sharing for tens of thousands of years the continent.
New techniques have been devised and these might come useful in future projects. Cro Magnon hominins will probably be the following hominin to be sequenced. It should be noted however that only DNA of recent hominins can be extracted. The publication of the genome will certainly prompt several studies that will be published in the coming years.
I remind all readers that recently Intute run a series of podcasts on archaeological sciences, aimed at students who may be interested in starting a career in that field. The interview with Mrs Keri Brown (University of Manchester) is specifically on DNA.