Denisova Cave (Russie) : Molar from Fourth Denisovan Extends “Meager” Fossil Record


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35594220362 ed2005ddc3Photographs of the Denisova 2 lower second molar in (A) occlusal, (B) mesial, (C) buccal, (D) lingual, (E) distal, and (F) apical views. Scientists estimate the molar found in the Denisova Cave in Siberia is older than previously studied Denisovan fossils. Credit: Slon et al. Sci. Adv. 2017; 3: e1700186 

Scientists studying a newly discovered molar from the Denisova Cave in Siberia estimate the tooth is at least 20,000 years older than previously examined Denisovan fossils. The finding has important implications for understanding hominin evolution and adds to the “meager Denisovan fossil record,” of just three other Denisovan individuals, the authors say. What’s more, the molar provides evidence that Denisovans were present for a longer time in the region, allowing for more potential mingling between Neanderthals and Denisovans. The poor preservation of the molar was a challenge for Viviane Slon, Svante Pääbo, and colleagues as they analyzed the tooth. Nonetheless, they were able to extract DNA and compare the sequence to other Denisovan samples, as well as Neanderthal and human DNA. Results suggested that the female owner of the deciduous tooth, or “baby tooth,” lived at least 100,000 years ago. This age would make the tooth one of the oldest hominin remains discovered in Central Asia to date. The DNA found in the tooth is consistent with low levels of diversity among DNA from all the Denisovan samples recovered from the cave, the authors say, comparable to the lower range of genetic diversity in modern human populations. It’s possible, however, the samples from the cave represent an isolated population and that the genetic diversity of Denisovans across their geographical range was greater. Additional Denisovan fossils from other locations are needed to more comprehensively gauge their genetic diversity, the authors add.

35632094761 6d663024e4Photographs of the Denisova 2 lower second molar in (A) occlusal, (B) mesial, (C) buccal, (D) lingual, (E) distal, and (F) apical views. The scale for all panels is 2.5 millimeters. The area sampled for ancient DNA analyses is marked by a gray circle in panel C. Credit: Slon et al. Sci. Adv. 2017; 3: e1700186

35375887970 f7871d9d0dPhylogenetic tree relating the Denisova 2 mitochondrial DNA with other Denisovan mitochondrial DNA sequences. The mitochondrial DNA from Sima de los Huesos was used as an outgroup. The schematic representations of the specimens are drawn to scale, shown in the lower right corner. Credit: Slon et al. Sci. Adv. 2017; 3: e1700186