The extinction of prehistoric megafauna like woolly mammoth, cave lion and woolly rhino at the end of the last ice age is often attributed to the spread of primitive humans globally. Although over hunting led to the destruction of some species, a study appeared August 13 in the journal. Current biology found that the extinction of the fleece rhino could have another cause: climate change. By sequencing ancient DNA from these 14 herbivores, the researchers discovered that the wool rhino population remained stable and diverse until only a few thousand years before it disappeared from Siberia. , when temperatures can rise too high for cold-adapted species.
“It was originally thought that humans appeared in northeastern Siberia fourteen or fifteen thousand years ago, around the time the fleece rhino went extinct. But recently, there have been some discoveries about the sites. Human’s older residence, of which the most famous are about thirty thousand “old age”, senior author Love Dalén, professor of evolutionary genetics at the Center for Paleontology, a joint venture between Stockholm University and the Swedish Museum of Natural History, said. “So the decline to the extinction of the wool rhino did not coincide much with the first human appearance in area. If there’s something, we actually see something like an increase in population size during this period. “
To find out about the size and stability of sheep wool rhino populations in Siberia, researchers studied DNA from tissue, bone and hair samples from 14 individuals. “We sequenced a complete nuclear genome to look at time and estimate population size, and we also sequenced fourteen mitochondrial genomes to estimate the effective population size of the subgenus. female, “first co-author Edana Lord, a PhD. student at the Center for Paleontology.
By looking at the heterozygous nature, or genetic diversity, of these genomes, researchers can estimate the sheep rhino populations for tens of thousands of years before they went extinct. First co-author Nicolas Dussex, a postdoctoral researcher at the Center for Pervasive Genetics, said: “We examined changes in population size and estimated inbreeding. “We found that after increasing population size at the beginning of the cold period 29,000 years ago, the population size of the wool rhino remained unchanged and at this time the rate of inbreeding was low. . “
This stability lasted until after humans began living in Siberia, in contrast to the possible decline if the wool rhino went extinct due to hunting. “That’s interesting,” Lord said. “We don’t really see a drop in population size after 29,000 years ago. The data we looked at was only 18,500 years ago, which is about 4,500 years before they went extinct, so that implies they are. has declined sometimes in that distance. “
The DNA data also revealed genetic mutations that help sheep rhinos adapt to colder weather. One of these mutations, a type of receptor on the skin that senses warm and cold temperatures, was also found in woolly mammoths. Adaptations like this suggest that the wool rhino, particularly suited to the cold northeastern Siberian climate, may have declined due to the heat of a short warming period, known as interstate. Bølling-Allerød state, which coincided with their extinction at the end of the last ice age.
“We are getting out of the idea of people taking over things as soon as they enter the environment, and instead shedding light on the role climate plays in the megafaunal extinctions,” Lord said. “Although we cannot rule out human involvement, we believe that the extinction of the fleece rhino is more likely to be climate related.”
The researchers hope to study the DNA of complementary wool rhinoceroses that lived within the critical 4,500 years gap between the last genome they decoded and their extinction. “What we want to do now is try to get more genomic sequences from rhinos between eighteen and fourteen thousand years old, because by some point they would definitely be,” Dalén said. must decline ”. The researchers are also looking at other cold-adapted megafauna to see what more effects a warmer, unstable climate has. “We know the climate has changed a lot, but the question is: how have different species of animals been affected, and what do they have in common?”
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Current biology, Lord et al.: “Pre-extinction demographic stability and genomic markers of adaptation in the wool rhino” www.cell.com/current-biology/f… 0960-9822 (20) 31071-X, DOI: 10.1016 / j. cub.2020.07.046
Quote: Ancient genomes showing that the fleece rhino was extinct due to climate change rather than over hunting (2020, August 13) retrieved August 13, 2020 from https: / /phys.org/news/2020-08-ancient-genomes-woolly-rhinos-extinct. html
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