THE DISAPPEARANCE OF WOOLLY RHINOCEROS IS NOT OUR FAULT: a new study by scientists
In science and public consciousness, the idea has taken hold that the disappearance of outlandish representatives of prehistoric megafauna at the end of the last Ice Age is associated with the resettlement of primitive people around the world and their intense hunting. A recently published study claims that the disappearance of woolly rhinos may have had another cause — climate change.The term “megafauna” is used to refer to the fauna of the era of the spreading of giant mammals — mammoth, Smilodon, cave bear, ground sloth, Glyptodon, Andrewsarchus, and so on. The megafauna of pedozoology means large (over 80 mm) invertebrates, as well as moles, snakes, turtles, rodents and other creatures that dig tunnels and passageways in soils.
The new study is spearheaded by Love Dalén, professor of evolutionary genetics at the Center for Paleogenetics, a brainchild of Stockholm University and the Swedish Royal Museum of Natural History.
A well-known specialist recalls: it was originally believed that people appeared in the northeast of Siberia 14,000 or 15,000 years ago, around the time when woolly rhinoceros became extinct. However, much older human habitats have recently been discovered, the oldest of which are about thirty thousand years old. Consequently, the decrease of woolly rhinos and their extinction do not overlap very clearly with the first appearance of humans in that region. Scientists have reconstructed the dynamics of population development and it seems that at that time there was just an increase in the number of animals.
To determine the size and stability of the woolly rhinoceros population in Siberia, the researchers examined the DNA of tissue, bone and hair samples from 14 individuals. Scientists have sequenced the complete nuclear genome, which allowed to determine the size of the population, and also sequenced fourteen mitochondrial genomes to examine the size of the female population.
By analyzing the genetic diversity of these genomes, the researchers were able to study changes in population size and evaluate inbreeding. Inbreeding is a form of homogamy, the crossing of closely related forms within the same population of organisms (animals or plants). The scientists found that after a population increase in the early cold season about 29,000 years ago, the amount of woolly rhinoceros remained stable and inbreeding was low.
Such stability persisted even after primitive people settled in Siberia, which casts doubt on the hypothetical blame for the disappearance of the species on the hunters.
The DNA data also revealed genetic mutations that allowed woolly rhinos to adapt to colder weather. One of these mutations, a type of skin receptor for sensing high and low temperatures, was also found in woolly mammoths. Based on such adaptations, it can be assumed that the woolly rhinoceros population, which was well adapted to the cold climate of northeastern Siberia, may have declined due to a short period of warming known as the Bølling-Allerød interstadial, from 14690 to 12890 BC.
The researchers plan to study the DNA of other woolly rhinos that lived in the crucial 4,500-year gap between the last genome sequenced and their disappearance. Love Dalén says:
We want to get more genomic sequences for rhinoceroses that are between 18,000 and 14,000 years old, because at some point they will surely show the process of population decline
Scientists are also going to study other representatives of the cold-adapted megafauna in order to establish what further consequences the warming and unstable climate had.
Ultimately, researchers will be able to answer the question: “How much have different animals suffered from climate change, and what do they have in common?”
Let us remind our readers that, in addition to the tragic disappearance as a species, the woolly rhinoceros had a difficult fate with its Latin name — scientists did not immediately come to a consensus on this score.
- In the 1770s, the German-Russian naturalist P. S. Pallas named it Rhinoceros lenensis (Latin: Rhinoceros — rhino, lenensis — Lena, from the name of the Lena River in Siberia).
- In 1799, the German naturalist J. F. Blumenbach gave the rhino the unpretentious name Rhinoceros antiquitatis (literally — ancient rhino).
- In 1831, the German paleontologist H. Bronn proposed a generic name — Coelodonta (cavity-toothed, with hollow teeth), which reflected the characteristic feature of the teeth of a woolly rhinoceros and for some time this name became common.
- In 1832, the famous French biologist J. Cuvier joined the search for an adequate name and proposed his own version – Rhinocerostichorinus (Greek: τυχοσ – wall, that is, a rhinoceros, whose nose is like a wall, which hinted at the presence of an ossified nasal septum).
Still, the name Rhinoceros antiquitatis — the ancient rhinoceros — stuck.
Edana Lord, Nicolas Dussex, Marcin Kierczak, David Díez-del-Molino, Oliver A. Ryder, David W.G. Stanton, M. Thomas P. Gilbert, Fátima Sánchez-Barreiro, Guojie Zhang, Mikkel-Holger S. Sinding, Eline D. Lorenzen, Eske Willerslev, Albert Protopopov, Fedor Shidlovskiy, Sergey Fedorov, Hervé Bocherens, Senthilvel K.S.S. Nathan, Benoit Goossens, Johannes van der Plicht, Yvonne L. Chan, Stefan Prost, Olga Potapova, Irina Kirillova, Adrian M. Lister, Peter D. Heintzman, Joshua D. Kapp, Beth Shapiro, Sergey Vartanyan, Anders Götherström, Love Dalén. Pre-extinction Demographic Stability and Genomic Signatures of Adaptation in the Woolly Rhinoceros.Current Biology, 2020; DOI: 10.1016/j.cub.2020.07.046