CELL PRESS
The extinction of prehistoric megafauna like the woolly mammoth, cave lion, and woolly rhinoceros at the end of the last ice age has often been attributed to the spread of early humans across the globe. Although overhunting led to the demise of some species, a study appearing August 13 in the journal Current Biology found that the extinction of the woolly rhinoceros may have had a different cause: climate change. By sequencing ancient DNA from 14 of these megaherbivores, researchers found that the woolly rhinoceros population remained stable and diverse until only a few thousand years before it disappeared from Siberia, when temperatures likely rose too high for the cold-adapted species.
“It was initially thought that humans appeared in northeastern Siberia fourteen or fifteen thousand years ago, around when the woolly rhinoceros went extinct. But recently, there have been several discoveries of much older human occupation sites, the most famous of which is around thirty thousand years old,” says senior author Love Dalén (@love_dalen), a professor of evolutionary genetics at the Centre for Palaeogenetics, a joint venture between Stockholm University and the Swedish Museum of Natural History. “So, the decline towards extinction of the woolly rhinoceros doesn’t coincide so much with the first appearance of humans in the region. If anything, we actually see something looking a bit like an increase in population size during this period.”
To learn about the size and stability of the woolly rhinoceros population in Siberia, the researchers studied the DNA from tissue, bone, and hair samples of 14 individuals. “We sequenced a complete nuclear genome to look back in time and estimate population sizes, and we also sequenced fourteen mitochondrial genomes to estimate the female effective population sizes,” says co-first author Edana Lord (@EdanaLord), a PhD student at the Centre for Palaeogenetics.
By looking at the heterozygosity, or genetic diversity, of these genomes, the researchers were able to estimate the woolly rhino populations for tens of thousands of years before their extinction. “We examined changes in population size and estimated inbreeding,” says co-first author Nicolas Dussex, a postdoctoral researcher at the Centre for Palaeogenetics. “We found that after an increase in population size at the start of a cold period some 29,000 years ago, the woolly rhino population size remained constant and that at this time, inbreeding was low.”
This stability lasted until well after humans began living in Siberia, contrasting the declines that would be expected if the woolly rhinos went extinct due to hunting. “That’s the interesting thing,” says Lord. “We actually don’t see a decrease in population size after 29,000 years ago. The data we looked at only goes up to 18,500 years ago, which is approximately 4,500 years before their extinction, so it implies that they declined sometime in that gap.”
The DNA data also revealed genetic mutations that helped the woolly rhinoceros adapt to colder weather. One of these mutations, a type of receptor in the skin for sensing warm and cold temperatures, has also been found in woolly mammoths. Adaptations like this suggest the woolly rhinoceros, which was particularly suited to the frigid northeast Siberian climate, may have declined due to the heat of a brief warming period, known as the Bølling-Allerød interstadial, that coincided with their extinction towards the end of the last ice age.
“We’re coming away from the idea of humans taking over everything as soon as they come into an environment, and instead elucidating the role of climate in megafaunal extinctions,” says Lord. “Although we can’t rule out human involvement, we suggest that the woolly rhinoceros’ extinction was more likely related to climate.”
The researchers hope to study the DNA of additional woolly rhinoceroses that lived in that crucial 4,500-year gap between the last genome they sequenced and their extinction. “What we want to do now is to try to get more genome sequences from rhinos that are between eighteen and fourteen thousand years old, because at some point, surely they must decline,” says Dalén. The researchers are also looking at other cold-adapted megafauna to see what further effects the warming, unstable climate had. “We know the climate changed a lot, but the question is: how much were different animals affected, and what do they have in common?”
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This work was supported by FORMAS, the Swiss National Science Foundation, the Carl Tryggers Foundation, the European Research Council Consolidator Award, and the Knut and Alice Wallenberg Foundation.
Current Biology, Lord et al.: “Pre-extinction demographic stability and genomic signatures of adaptation in the woolly rhinoceros” https://www.cell.com/current-biology/fulltext/S0960-9822(20)31071-X
Current Biology (@CurrentBiology), published by Cell Press, is a bimonthly journal that features papers across all areas of biology. Current Biology strives to foster communication across fields of biology, both by publishing important findings of general interest and through highly accessible front matter for non-specialists. Visit: http://www.cell.com/current-biology. To receive Cell Press media alerts, contact press@cell.com.
It is generally thought that those were not modern humans. The best evidence is that modern humans left Africa less than 100K years ago.
Several big bits of a comet impacting north America probably did not help them!
Since there’s no evidence of that happening and all the evidence in the world against it, the effect was presumably minimal.
There is evidence of an impact in South America. … https://www.nature.com/articles/s41598-018-38089-y
It is possible that there were several fragments which hit at multiple locations around the same time. What would happen in a smaller fragment landed on the remnants of the melting continental ice sheets in North America/Greenland? Would we see a crater, or would there just be a massive melting of the ice sheet, and a beyond huge mass of steam/water vapor thrown high into the atmosphere which would then steadily rain out for many months afterwards? Could that have been the cause of the biblical flood? A flood which did flood all land surfaces at all elevations for some period of time?
An event of that magnitude could explain why mankind went underground in many locations around the world. There are quite a few stories that state that humanity came from the caves.
Cute video about curly horses.
(7 min.)
It seems unlikely that the moderate warmth of the 1,800-year-long Bølling-Allerød interstadial could kill off a species which survived the greater warmth of the 20,000-year-long Eemian. But what do I know?
No one can convince me that Woolly Rhino’s did not go extinct because Cave Men thought they looked hot in a Woolly Rhino coat.
Honestly, I wish so-called scientists would grow up. They almost certainly did not go extinct for a single reason but instead a range of changes that they were ill suited to. Temperature, foraging, disease, predators…it was likely all of there to some degree. Why we need to blame ONE THING I don’t understand, but that seems to be the fade.
Not many people realise that the woolly rhino actually lived in a very mild, temperate climate. Quite similar to today’s climate.
That is why they needed a thick woolly coat.
When the climate became warmer, they all overheated and died. Not because of climate change, but because they never invented scissors, which would have allowed them to cut their thick woolly coats.
And even if they had invented scissors, that would not have saved them. Because evolution did not equip them with opposable thumbs, which are needed to use scissors.
Woolly rhinos died out because there was a world shortage of hairdressers.
Sheldon
Yes, all the hairdressers had left on the B Ark.
Maybe a viral pandemic wiped them out.
Guys using pointy stones hundred the RHINO to extinction. I want to be on their team. Hey, Aubrey, after lunch, go kill a rhino for us….