Climate Change Didn't Cause the Mass Extinction After the Last Ice Age--Humans Did
Climate change may not be behind an extinction event that occurred around the time of the last Ice Age. Instead, humans may be to blame. Scientists have carried out the first global analysis of the extinct of large mammals and have found that our ancient ancestors may be the main cause behind this event.
Immediately after the last Ice Age, large animals, called megafauna, were prevalent. Yet many of these large animals became extinct. Researchers have long wondered whether these large animals became extinct due to climate change, or if there were other factors at play-especially because during previous Ice Ages, these large animals didn't die off.
In order to find out whether humans might be to blame, the researchers produced the first global analysis and relatively fine-grained mapping of all of the large mammals that existed during the period 132,000 to 1,000 years ago. That's the period during which the mass extinction took place. This allowed them to study the geographical variation in the percentage of large species that became extinct on a much finer scale than previously managed.
So what did they find? It turns out that a total of 177 species of large mammals disappeared during this mass extinction. Africa lost 18 species, Europe lost 19, Asia lost 38, Australia lost 26, North America lost 43 and South America lost 62.
So what does this mean? It turns out that the extinction impacted large animals that occurred in all climate zones. It affected cold-adapted species, like woolly mammoths, but also impacted temperate species, such as forest elephants and giant deer, and even tropical species, such as giant sloths. This seems to show that climate wasn't necessarily the major cause. In fact, the scientists found that the variation in temperature and precipitation only really affected on area's megafauna-namely Eurasia.
"The significant loss of megafauna all over the world can therefore not be explained by climate change, even though it has definitely played a role as a driving force in changing the distribution of some species of animals," said Christopher Sandom, one of the researchers, in a news release. "Reindeer and polar foxes were found in Central Europe during the Ice Age, for example, but they withdrew northwards as the climate became warmer."
In fact, the researchers found a very strong correlation between the extinction and the history of human expansion. There were large rates of extinction in areas where there had been no contact between megafauna and humans, and then the animals were suddenly confronted by humans.
The findings reveal the prevalence of human impact in the ancient world; it also has relevance for current human impacts. Poaching and hunting is having a large effect on the animals of the world today, and could drive populations to extinction if steps aren't taken.
The findings are published in the journal Proceedings of the Royal Society B.