Our Hybrid DNA: Important Concepts and Names
2. The Denisova Cave is located in southwestern Siberia, in the Altai Mountains near the border with China and Mongolia. It is named after Denis, a Russian hermit who lived there in the 18th century. The cave was originally explored in the 1970s by Russianpaleontologist Nikolai Ovodov, who was looking for remains of cave bears. In 2008, Michael Shunkov from the Russian Academy of Sciences and other Russian archaeologists from the Institute of Archaeology and Ethnology of Novosibirsk investigated the cave. They found the finger bone of a juvenile hominin, dubbed the "X woman" (referring to the maternal descent of mitochondrial DNA) or the Denisova hominin. Artifacts, including a bracelet, excavated in the cave at the same level were carbon dated to around 40,000 BP. Excavations have since revealed human artifacts showing an intermittent presence going back 125,000 years. A team of scientists led by Johannes Krause and Svante Pääbo from the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, sequenced mtDNA extracted from the fragment. The cool climate of the Denisova Cave preserved the DNA. The average annual temperature of the cave remains at 0 °C, which has contributed to the preservation of archaic DNA among the remains discovered. The analysis indicated that modern humans, Neanderthals, and the Denisova hominin last shared a common ancestor around 1 million years ago. The mtDNA analysis further suggested that this new hominin species was the result of an earlier migration out of Africa, distinct from the later out-of-Africa migrations associated with modern humans, but also distinct from the earlier African exodus of Homo erectus. Pääbo noted that the existence of this distant branch creates a much more complex picture of humankind during the Late Pleistocene. This work shows that the Denisovans were actually a sister group to the Neanderthals, branching off from the human lineage 600,000 years ago, and diverging from Neanderthals, probably in the Middle East, 200,000 years later. Later in 2010, a second paper from the Svante Pääbo group reported the prior discovery, in 2000, of a third upper molar from a young adult, dating from about the same time (the finger was from level 11 in the cave sequence, the tooth from level 11.1). The tooth differed in several aspects from those of Neanderthals, while having archaic characteristics similar to the teeth of Homo erectus. They performed mitochondrial DNA analysis on the tooth and found it to have a sequence different from but similar to that of the finger bone, indicating a divergence time about 7,500 years before, and suggesting that it belonged to a different individual from the same population. In 2011, a toe bone was discovered in the cave, in layer 11, and therefore contemporary with the finger bone. Preliminary characterization of the bone's mitochondrial DNA suggests it belonged to a Neanderthal, not a Denisovan. The cave also contains stone tools and bone artifacts made by modern humans, and Pääbo commented: "The one place where we are sure all three human forms have lived at one time or another is here in Denisova Cave."
3. INTERBREEDING. A detailed comparison of the Denisovan, Neanderthal, and human genomes has revealed evidence for a complex web of interbreeding among the lineages. Through such interbreeding, 17% of the Denisova genome represents DNA from the local Neanderthal population, while evidence was also found of a contribution to the nuclear genome from an ancient hominin lineage yet to be identified, perhaps the source of the anomalously ancient mtDNA. Analysis of genomes of modern humans show that they mated with at least two groups of ancient humans: Neanderthals (more similar to those found in the Caucasus than those from the Altai region) and Denisovans. Approximately 4% of the DNA of non-African modern humans is shared with Neanderthals, suggesting interbreeding. Tests comparing the Denisova hominin genome with those of six modern humans – a ǃKung from South Africa, a Nigerian, a Frenchman, aPapua New Guinean, a Bougainville Islander and a Han Chinese – showed that between 4% and 6% of the genome of Melanesians (represented by the Papua New Guinean and Bougainville Islander) derives from a Denisovan population. This DNA was possibly introduced during the early migration to Melanesia. These findings are in concordance with the results of other comparison tests which show a relative increase in allele sharing between the Denisovan and the Aboriginal Australian genome, compared to other Eurasians and African populations; however, it has been observed that Papuans, the population of Papua New Guinea, have more allele sharing than Aboriginal Australians.
4. Svante Pääbo is a Swedish biologist specializing in evolutionary genetics. One of the founders of paleogenetics, he has worked extensively on the Neanderthal genome. Born in Stockholm, 20 April 1955, Pääbo is the son of Estonian chemist Karin Pääbo and biochemist Sune Bergström. Growing up with his mother, he barely knew his father, who shared the Nobel Prize in Physiology or Medicine with Bengt I. Samuelsson and John R. Vane in 1982. He earned his PhD from Uppsala University in 1986. Since 1997, he has been director of the Department of Genetics at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany. Pääbo is known as one of the founders of paleogenetics, a discipline that uses the methods of genetics to study early humans and other ancient populations. In 1997, Pääbo and colleagues reported their successful sequencing of Neanderthalmitochondrial DNA (mtDNA), originating from a specimen found in Feldhofer grotto in the Neander valley. In August 2002, Pääbo's department published findings about the "language gene", FOXP2, which is lacking or damaged in some individuals with language disabilities. In 2006, Pääbo announced a plan to reconstruct the entire genome of Neanderthals. In 2007, he was named one of TIME Magazine's 100 most influential people of the year. In February 2009, at the Annual Meeting of the American Association for the Advancement of Science (AAAS) in Chicago, it was announced that the Max Planck Institute for Evolutionary Anthropology had completed the first draft version of the Neanderthal genome. Over 3 billion base pairs were sequenced in collaboration with the 454 Life Sciences Corporation. This project, led by Pääbo, will shed new light on the recent evolutionary history of modern humans. In March 2010, Pääbo and his coworkers published a report about the DNA analysis of a finger bone found in the Denisova Cave in Siberia; the results suggest that the bone belonged to an extinct member of the genus Homo that had not yet been recognized, the Denisova hominin. In May 2010, Pääbo and his colleagues published a draft sequence of the Neanderthal genome in the journal Science. He and his team also concluded that there was probably interbreeding between Neanderthals and Eurasian (but not African) humans. There is growing support in the scientific community for this theory of admixture between archaic and anatomically-modern humans, though some archaeologists remain skeptical about this conclusion. In 2014, he published the book Neanderthal Man: In Search of Lost Genomes where he in the mixed form of a memoir and popular science tells the story of the research effort to map the Neanderthal genome combined with thought on human evolution. In 1992, he received the Gottfried Wilhelm Leibniz Prize of the Deutsche Forschungsgemeinschaft, which is the highest honour awarded in German research. Pääbo was elected a member of the Royal Swedish Academy of Sciences in 2000. In October 2009 the Foundation for the Future announced that Pääbo had been awarded the 2009 Kistler Prize for his work isolating and sequencing ancient DNA, beginning in 1984 with a 2,400-year-old mummy. In June 2010 the Federation of European Biochemical Societies awarded him the Theodor Bücher Medal for outstanding achievements in Biochemistry and Molecular Biology. In 2013, he received Gruber Prize in Genetics for ground breaking research in evolutionary genetics. ------- Svante Pääbo has developed techniques and approaches that allow DNA sequences from archaeological and paleontological remains to be determined. This has allowed ancient DNA from extinct organisms, humans, animals and pathogens to be studied. He determined a high-quality Neandertal genome sequence, allowing for the reconstruction of the recent evolutionary history of our species and the realization that Neandertals contributed DNA to present-day humans who live outside Africa. By studying DNA sequences from a small Siberian bone he discovered Denisovans, a previously unknown hominin group distantly related to Neandertals. He also works on the comparative and functional genomics of humans and apes, particularly the evolution of genetic features such as the FOXP2 ‘speech and language’ gene that may underlie aspects of traits specific to humans. Svante Pääbo has received several honorary doctorates and scientific prizes and is a member of numerous academies. He is currently a Director at the Max-Planck Institute for Evolutionary Anthropology in Leipzig, Germany.
5. DNA. In all animals, DNA is found in two places: In the nucleus of every cell (except red blood cells, which contain no nucleus or DNA and therefore cannot be affected by viruses) and in mitochondria, small organelles that act as the “batteries” which power individual cells. The 46 chromosomes in a human cell are actually long strands of DNA that have segments called genes. The DNA in a nucleus and the DNA in mitochondria together form the genome of a person/organism.
6. HOMININ vs. HOMINID• Hominid – the group consisting of all modern and extinct Great Apes (that is, modern humans, bonobos, chimpanzees, gorillas, and orangutans plus all their immediate ancestors). • Hominin – the group consisting of modern humans, extinct human species and all our immediate ancestors (including members of the genera Homo, Australopithecus, Paranthropus and Ardipithecus).• Great apes—species in the biological family Hominidae, including humans, bonobos, chimpanzees, gorillas, and orangutans.
- INSTITUTE FOR HUMAN ORIGINS (Arizona State University): https://iho.asu.edu/
- EVOLUTION OF HUMAN SKIN AND PIGMENATION (Penn State): https://anth.la.psu.edu/people/ngj2
- HUMAN EVOLUTION (Smithsonian Natural History Museum): https://humanorigins.si.edu/research
- HUMAN ORIGINS (American Museum of Natural History): https://www.amnh.org/exhibitions/permanent/human-origins
Web Resources about Interbreeding
- SVANTE PAABO: http://www.eva.mpg.de/genetics/staff/paabo/cv.html?Fsize=%27A%3D00
- SVANTE PAABO: http://www.theguardian.com/science/2014/feb/15/svante-paabo-dna-neanderthal-genetics
- SVANTE PAABO (video): https://www.youtube.com/watch?v=gJLI3N5dovw&t=189s
- DENISOVANS: http://ngm.nationalgeographic.com/2013/07/125-missing-human-ancestor/shreeve-text
- PAABO AND DENISOVANS (video): https://www.youtube.com/watch?v=MjMoQDTIzTY SVANTE PAABO (video): https://www.youtube.com/watch?v=gJLI3N5dovw