New genetic evidence suggests it was a warming climate–not human human overloadwho killed rhinos wool at the end of the last ice age.
with cave bears, to knowdirected cats, woolly mammoths, giant carats, and wild wolves, the Pleistocene was a shell of megafaunal pleasures. And of course, there was the wool rhino (Old Coelodonta), an incredibly large and harsh version of the horned beasts we are accustomed to today.
Weighing over 4,500 pounds (2,000 kg) and containing a giant shoulder lump, these impressive herbivores conquered vast territory stretching from western Europe in North Asia. The reign of wool rhinos, which lasted for millions of years, came to an abrupt end about 14,000 years ago, with Siberia as the last place of their long stay on Earth.
Human overload and the end of the last ice age are the two causes commonly attributed to their death, though a full understanding of the reasons for their disappearance is quite lacking. New genetic evidence published today in Current Biology is adding color to this shocking period of our planet’s evolutionary history, showing that it was climate change that end this species.
With their colleagues, researchersEdana Lord and Nicolas Dussex from the Center for Paleogenetics – a joint venture between Stockholm University and the Swedish Museum of Natural History – sequence the genome of 14 furry rhinos, extracting DNA from preserved tissues, bones and hair samples. The team compiled estimates of rhino population sizes over time by sequencing a complete nuclear genome and collecting over a dozen mitochondrial genomes, the latter technique providing an estimate of the female population sizes.
Combined, this genetic data provided a picture of the wool rhinos from approximately 29,000 years ago to 18,500 years ago. As the authors in the study show, the wool rhinos population was extremely stable and diverse over thousands of years leading up to their extinction. If anything, new data suggests that these animals were actually doing quite well over time millennia leading to the end of the last ice age.
“We do not actually see a decrease in population size after 29,000 years ago,” Lord explained in a Cell Press release. “The data we just looked at goes back to 18,500 years ago, which is roughly 4,500 years before they disappeared, so that means they fell somewhere in that gap.”
“It’s not something we’ve known before and shows that the decline towards extinction occurred quite close to the final extinction of the species, “Love Dalén, senior author of the study and an evolutionary geneticist at the Center for Palaeogenetics, explained in an email.
The new DNA analysis also revealed special adaptations to the cold, such as an enhanced ability to sense warm and cold temperatures. These animals also exhibited higher genetic diversity than woolly mammoths and rhinos still around today.
These data do not go well with the idea that ice age human hunters drove wool rhinos to extinction. Humans, as we are learning, were active in North Asia about 30,000 years ago, long before the extinction of this species. Moreover, the apparent durability of fur rhinos during this expansive period suggests that humans played a small, if not negligible, role in their destruction.
“We found that after an increase in population size at the beginning of a cold period about 29,000 years ago, the size of the wool root population remained constant and that at this time, inbreeding was low,” Dussex explained in the announcement. for the press.
This birth was low is quite revealing, as the lack of genetic diversity is an indicative sign of a species in big trouble. Just ask wool giants.
Sure, it is possible that people still played a role in their disappearance, but Dalén thinks it is unlikely.
“In a way, I think it ‘s not very surprising that we do not see an effect of human arrival,” he said. “One two-tons of armored beast, with a 1.5-meter horn and a bad temperament, is probably not something that Paleolithic people would have been so eager to poking with a spear. “
Indeed, this work raises an important point, in that people are often blamed for extinctions that occurred in the late Upper Paleolithic. For these tiny groups of people struggling to survive in the harsh environment of the ice age, it seems they may suggest that they may wipe out entire species of giant herbivores, be they woolen sleeves or woolly mammoths. Dalén agrees.
“I personally think it is unlikely that humans back then had the ability to just hunt an endangered species, except on small islands,” he said. “The main reason is that once a favorite prey becomes rare, predators tend to switch to another species of prey. Also, for really large ones, such as rhino and mammoth, it seems to me that the danger and difficulty of hunting these animals would have been too large to be made on an ‘industrial’ scale. “
That said, we know that early humans in Siberia hunted much smaller herbivores, such as the Stepon bison, the strong-legged horse, the reindeer, and the muskox.
“Although I do not think humans could have just pushed these to extinction, it certainly seems plausible that a combination of human hunting and climate change-driven environmental change may have led to extinction, for example, the ice age. with strong legs bison horse and steppe, “said Dalén.
As for how the changing climate made life so difficult for rhino-wool, this remains an unanswered question. Heating temperatures between 14,700 and 12,900 years ago resulted in increased rainfall, turning the open steppe into a bushy environment.
“Personally, my hypothesis is that the change in rainfall may have been a major force, as this may have led to increased humidity during the summer, resulting in more swamps and bumps, and increased snow cover in winter, making it harder to find food if you are a kidnapper, “Dalén explained.
In terms of future work, the team would like to get more DNA out of that arduous gap between 18,000 and 14,000 years ago – clearly a time when something quite unfortunate started to happen rhinos wool.