Thursday 30 October 2008
CEA
The Chauvet Cave bears:from cave paintings to genomics analysis
CEA
Researchers from the CEA Institut of Biotechnology–Saclay (iBiTec-S) and a multidisciplinary team involving researchers from the CNRS tasked with analyzing the Chauvet-Pont d’Arc Cave have announced that starting with a bone from the cave, they have been able to sequence the mitochondrial DNA of the cave bear, a species that has been extinct for 15,000 years. These genomics analyses have demonstrated that the last common ancestor to the cave bear and the brown bear walked the Earth around 1.6 million years ago. The results of this research have just been published in the 27th October issue of the Proceedings of the National Academy of Sciences of the USA.
Although primary known for its exceptional cave paintings, Chauvet-Pont d’Arc Cave, which is controlled and protected by the French Ministry for Culture and Media Studies as a historical monument, is equally significant as a site where cave bear bones have been unearthed. Carbon-14 dating has shown that cave bears were using the cave site 32,000 years ago. These bones were so exceptionally well-preserved that the biologists have been able to analyze the trace DNA, and thus make breakthroughs in the study of extinct species and the phylogenetics[1] of the bear.
Drawing of a cave bear in Chauvet-Pont d’Arc Cave; © Ministry for Culture and Media Studies, DRAC Rhône-Alpes, SRA
and bones being prepared for sampling; © M.-A. Garcia.
and bones being prepared for sampling; © M.-A. Garcia.
The mitochondrion contains DNA that is smaller than the DNA found in the cell nucleus, and this mitochondrial DNA gives precise data on the evolutionary history of organisms. It acts like a 'molecular clock', timing the juncture in history at which two species diverged. However, DNA is not conserved infinitely over time, and to date, researchers looking to analyze the mitochondrial DNA from cave bears mostly had only tiny fragments to work with. The team of iBiTec-S biochemists pinpointed a biological specimen that contained exceptionally well-preserved genetic material. They then purified, amplified and sequenced this specimen's DNA, a process that allowed them to characterize a complete mitochondrial genome that counted 17,000 nucleotides. This genome could then be cross-compared against the genome of bears alive today to phylogenetically map the bear's evolutionary ancestry. The findings demonstrate that the last common ancestor to the cave bear and its closest relative, the contemporary brown bear, walked the Earth around 1.6 million years ago.
The osteometric carbon-14 dating brought together physicists, archaeologists and palaeontologists. The genomics analysis that has just been completed is a spectacular illustration of the role that biologists are ready to play in studying important historical sites. The Chauvet Cave research team was created with this kind of cross-discipline approach in mind.
This research was funded by the CEA and the French Ministry for Culture and Media Studies
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Article reference :
Bon C, Caudy N, de Dieuleveult M, Fosse P, Philippe M, Maksud F, Beraud-Colomb E, Bouzaid E, Kefi R, Laugier C, Rousseau B, Casane D, van der Plicht J, Elalouf JM (2008) Deciphering the complete mitochondrial genome and phylogeny of the extinct cave bear in the Paleolithic painted cave of Chauvet.Proc. Natl. Acad. Sci. online the 27th of october 2008.
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