Denisovans

Olivia Smith

Background

Denisovans are named after Denisova Cave, the primary location where related fossils were found. This cave is located in the Altai Mountains of Siberia, Russia. Other than Denisovan fossils, the Denisova Cave was also home to the remains of multiple other hominin species (Kuzmin et al., 2022).

Despite the difference in location, a mandible was discovered at the Baishiya Cave in Xiahe, China. Researchers identified the mandible as a Denisovan fossil, although there was a time of uncertainty regarding this classification. The mandible is known to be the earliest recorded human presence on the Tibetan Plateau.

At least two distinct Denisovan populations contributed significantly to the gene pool of modern populations, particularly in East Asia and Oceania. Traces of this can be found in people in Japan, China, and other parts of East Asia (Peyrégne et al,. 2024).

Defining Features

Since there is such a small amount of well-preserved fossils for this species, there is still much we do not know about Denisovans. What we do know is that despite their relation to Neanderthals, genetic evidence still suggests they were a distinct species (Zeberg et al., 2024). Much of the knowledge we have of the physical characteristics of Denisovans has been found from their DNA. From genetic data we have gathered that Denisovans may have dark skin, hair, and eyes. Currently, we do not have any information on their stature or body size. There has not yet been a specimen recognized as Denisovan based on physical characteristics (Zhang et al., 2021).

Molar from Denisova 2

With the molars, it is worth noting that they lack the derived traits commonly found with Neanderthals. They are larger in scale, as well as having a longer tooth row, and do not resemble the molars of a modern human. In addition to this, what we know of the mandible was strongly built and shorter than those of Neanderthals (Zeberg et al., 2024).

Some researchers speculate that Denisovans descended from a lineage Homo erectus having traveled from Africa to Eurasia. Other than this information, we are still unsure exactly where the Denisovans fit into the taxonomy of human evolution. Other evidence suggests that Denisovans are descended from Homo heidelbergensis, or rather share a common ancestor with them (Peyrégne et al,. 2024).

Evolutionary Tree

Denisovans share a common ancestor with Neanderthals, having diverged from them around 440-390 kya. This information was discovered using the high-coverage nuclear genome of one of the fossils found (Zhang et al., 2021). Denisovans and Neanderthals coexisted until about 40 thousand years ago, with evidence suggesting that the two species interbred. This relationship goes so far that Denisovans have also been referred to as a sister population to Neanderthals (Kuzmin et al., 2022).

Fossils

The Xiahe mandible was found at the Baishiya Cave in Xiahe, China. This is known to be the first discovery of a fossil containing Denisovan DNA that has been found outside of the Denisova cave in Russia. There was much hesitance around the classification of the mandible due to the fact that its identification is based on the position of an amino acid. The high altitude of the cave leads researchers to believe Denisovans may have developed adaptations to allow them to inhabit this area (Zhang et al., 2020).

Very few and highly fragmented fossils have been found from Denisovans. The fossils found so far have been incomplete molars, partial phalanges, small bone chips, and a mandible. These fossils were found in sediment layers alongside stone tools and animal bones. What we now assume to be scrapers made out of river sediments were the primary stone tools associated with the Denisovan fossils (Kuzmin et al., 2022).

Denisova 3 was the first fossil to be identified, having been found in 2008. It was discovered by a team of researchers led by Michael Shunkov. The fossil consisted of partial phalanges, with the growth plate on the bone not yet fused. This indicates the fossil belonged to a female child. She was then dubbed X-Woman. This fossil was one of the most important in identifying the Denisovan population through DNA sequencing (Zeberg et al., 2024).

Denisova 11 was also thought to be a younger female, found in 2012. This specimen is also known as Denny and was discovered by Michael Shunkov and Svante Pääbo. From her fossils, we were able to discover equal amounts of Neanderthal and Denisovan ancestry (Zhang et al., 2021). The question is whether this is because of a mixed population between the two species or because her parents were each from one of the groups.

Denisova 2, a molar found in 1984, is thought to be one of the oldest remains found in the Denisova Cave. This fossil was discovered by paleontologist Nikolai Ovodov. The crown is trapezoidal and tapers away from the center, with bulging lingual and buccal walls giving the tooth an inflated appearance The roots are short but robust and strongly flaring. The characteristics of this molar could indicate a diet that included tough, fibrous foods (Peyrégne et al,. 2024).

Partial phalanges from Denisova 3

Small bone chips from Denisova 11

Mandible from the Baishiya Cave

References

Kuzmin, Y. V., Slavinsky, V. S., Tsybankov, A. A., & Keates, S. G. (2022). Denisovans, Neanderthals, and Early Modern Humans: A Review of the Pleistocene Hominin Fossils from the Altai Mountains (Southern Siberia). Journal of Archaeological Research, 30(3), 321. https://doi.org/10.1007/s10814-021-09164-2

Peyrégne, S., Slon, V., & Kelso, J. (2024). More than a decade of genetic research on the Denisovans. Nature Reviews Genetics, 25(2), 83-103. https://doi.org/10.1038/s41576-023-00643-4

Zhang, D., Xia, H., Chen, F., Li, B., Slon, V., Cheng, T., Yang, R., Jacobs, Z., Dai, Q., Massilani, D., Shen, X., Wang, J., Feng, X., Cao, P., Yang, M. A., Yao, J., Yang, J., Madsen, D. B., Han, Y., & Ping, W. (2020). Denisovan DNA in Late Pleistocene sediments from Baishiya Karst Cave on the Tibetan Plateau. Science, 370(6516), 584–587. https://doi.org/10.1126/science.abb6320

Zhang, X., Witt, K. E., Bañuelos, M. M., Ko, A., Yuan, K., Xu, S., . . . Huerta-Sanchez, E. (2021). The history and evolution of the Denisovan- EPAS1 haplotype in Tibetans. Proceedings of the National Academy of Sciences of the United States of America, 118(22), 1.

Zeberg, H., Jakobsson, M., & Paabo, S. (2024). The genetic changes that shaped Neandertals, Denisovans, and modern humans. Cell, 187(5), 1047-1058. https://doi.org/10.1016/j.cell.2023.12.029

Page updated

Report abuse