Extinct cave bear yields its DNA
The cave bear became extinct 15,000 years ago, towards the end of the last Ice Age. A group of researchers have managed to isolate mitochondrial DNA from the breastbone of the bear species, which according to Prof. Hans van der Plicht dates from 32,000 years ago. The researchers publish their findings this week in PNAS Online Early Edition.
Image: A cave bear drawn in red ochre, approx. 80 cm in length.
There have already been successful efforts to reconstruct the DNA of extinct animal species. The hunt for ancient DNA started some twenty years ago with the quagga - a species of zebra, the last remaining specimen of which died in 1883 in Artis. Complete sequences of mitochondrial DNA have so far only been deciphered in the moa, a large New Zealand flightless bird which died out a few hundred years ago. Unlike other DNA, mitochondrial DNA (mtDNA) cannot be found in the cell nucleus and is only passed on through the female line. The mtDNA of such species as the woolly mammoth and the mastodon, which lived in the Pleistocene era and of which a large amount of material has been preserved in permafrost soil, has also already been deciphered.
Image: Pieces of charcoal were found under the skull of a cave bear. This means that the skull was placed there after the cave drawings were made.
Only skeletal remains survive of the cave bear (Ursus spelaeus). These bones are often found in caves which are used by humans. The scientists conducted their research on a breastbone found in the cave at Chauvet Pont d’Arc in Southern France. The oldest known rock paintings, including those of the cave bear, were also found in this cave. The cave bear bone was dated by Van der Plicht using the C14 method, and is estimated to be 31,870 years old, with a margin of error of approximately 300 years. Van der Plicht is the head of the C14 lab of the University of Groningen and also professor by special appointment in Isotope Archaeology at Leiden University.
Image: In the course of the years a stalagmite has developed on the skull of a cave bear.
The paintings in the cave are unique, having been dated at some 30,000 years old. Van der Plicht: ‘This is spectacularly old according to experts on the Stone Age; impossibly old, even, according to some sources. The subject has fuelled years of heated debate.' Until the discovery of this cave in 1994, it was generally assumed that paintings exhibiting such a high degree of artistry could not be more than 15,000 years old. The age of the paintings was also determined using the C14 method, but by a different team. 'Because there was some doubt about these datings,' explains Van der Plicht, 'charcoal from the open hearths in the cave was sampled and dated. This is what I am responsible for. My research is not so much about the paintings themselves, but about the charcoal with which the paintings were probably made.'
Image: This painting covers more than 6 m2 of wall space. The wall was first scraped clean, erasing earlier paintings. The different drawings were then added one after the other; a dark ox moving off to the left, a dark long-haired rhinoceros, a line drawing of two rhinoceros facing one another (C14 dated at 31,000 years old) and four horseheads. At the bottom, a small bison completes the picture.
The mtDNA provides a reliable revolutionary clock. Minor mutations in this DNA occur with a known frequency. This means that based on the number of mutations, it is possible to determine when two populations of the same species - or two species - began to diverge in their development. By comparing the mtDNA of the cave bear with that of the (western) brown bear (Ursus arctos), the researchers have been able to deduce that the two are sister species which started to develop separately from one another 1.6 million years ago. In comparison, it was just 400,000 years ago that the polar bear (Ursus maritimus) split off from the western brown bear.
This research is the first instance of DNA from a carnivore from the Pleistocene period being deciphered, although the cave bear was probably mainly ate vegetation. The researchers have brought the reconstruction of the family tree of the bear species a significant step further. They have also demonstrated that archaeological finds of skeletal material that was previously rejected as being unusable, can certainly be used for this type of DNA research.
Deciphering the complete mitochondrial genome and phylogeny of the extinct cave bear in the Paleolithic painted cave of Chauvet
Céline Bon, Nicolas Caudy, Maud de Dieuleveult, Jean-Marc Elalouf, Christelle Laugier, Bernard Rousseau, Philippe Fosse, Michel Philippe, Frédéric Maksud, Eliane Beraud-Colomb, Eric Bouzaid; Rym Kefi, Didier Casane, Johannes van der Plicht