Denisova Cave is located in the Altai mountains of Russia. Excavations from this cave have yielded two large hominin molars and three hominin phalanxes from the Pleistocene. One of the phalanxes (Denisova 3) had extraordinary DNA preservation allowing the sequencing of high quality nuclear and mitochondrial DNA (mtDNA) genomes and has been shown to belong to a young girl from hereto unknown sister group of Neandertals, called Denisovans. The mtDNA of Denisova 3 surprisingly split from the mtDNA ancestor of modern humans and Neandertals twice as long ago as the split of modern humans and Neandertals. The mtDNA of one of the molars (Denisova 4) was also sequenced and differs at only two positions from the mtDNA of Denisova 3. A second phalanx (Altai 1) also yielded a high quality genome, and was a Neandertal. While Neandertals show an admixture signal of 1-4% into present-day non-Africans, Denisovans show an admixture of up to 5% in present-day Oceanians, and to a much lesser extent East Asians.
This thesis encompasses two studies. In the first study, we sequenced the complete mtDNA genome of the additional molar (Denisova 8), as well as a few megabases of nuclear DNA from Denisova 4 and Denisova 8. While the mtDNA of Denisova 8 is clearly of the Denisova type, its branch to the most recent common ancestor of Denisovans is half as long as the branch leading to Denisova 3 or Denisova 4, indicating that Denisova 8 lived many millenia before the other two. Both Denisova 4 and 8 fall together with Denisova 3 based on nuclear DNA, bringing the number of known Denisovans from one to three.
In the second study, we sequenced an almost complete mtDNA and a few megabases of nuclear DNA from the third hominin phalanx from Denisova Cave, Altai 2. Both the mtDNA and the nuclear DNA show Altai 2 to be a Neandertal. The mtDNA also showed the presence of substantial Pleistocene spotted hyena contamination. Low levels of spotted hyena contamination were also found in Altai 1, Denisova 3 and Denisova 4. Partial mtDNA genomes of the contaminating spotted hyenas from these four hominins were compared to mtDNA genomes of other extant and extinct spotted hyenas. We show that the spotted hyenas that contaminated the two Denisovans come from a population of spotted hyenas found in Pleistocene Europe as well as present-day Africa, while the spotted hyenas that contaminated Altai 2, and possibly Altai 1, come from a population of spotted hyenas found in Pleisticene eastern Russia and northern China. This indicates that Denisova Cave was a meeting point of eastern and western hominins as well as eastern and western spotted hyena populations.
| Identifer | oai:union.ndltd.org:DRESDEN/oai:qucosa:de:qucosa:14757 |
| Date | 04 August 2016 |
| Creators | Sawyer, Susanna |
| Contributors | Pääbo, Svante, Universität Leipzig |
| Source Sets | Hochschulschriftenserver (HSSS) der SLUB Dresden |
| Language | English |
| Detected Language | English |
| Type | doc-type:doctoralThesis, info:eu-repo/semantics/doctoralThesis, doc-type:Text |
| Rights | info:eu-repo/semantics/openAccess |
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