A new study revealed that humans’ earliest tool-bearing ancestors had not caused the disappearance of large mammals in different areas around the world. In particular, ancient humans are not guilty of mammal extinction across Africa, affecting the continent over the last several million years. The scientists now consider that long-lasting environmental change triggered by significant drops in atmospheric carbon dioxide (CO2) levels is the main reason behind massive animals extinction.
“Despite decades of literature asserting that early hominins impacted ancient African faunas, there have been few attempts to actually test this scenario or to explore alternatives. We think our study is a major step towards understanding the depth of anthropogenic impacts on large mammal communities and provides a convincing counter-argument to these long-held views about our early ancestors,” said Tyler Faith from the Natural History Museum of Utah and the University of Utah.
To study the impact of ancient humans on mammal extinctions across Africa, the scientists studied a seven-million-year record of herbivore extinctions in eastern Africa.
Ancient Humans Are Not Guilty Of Mammal Extinctions Across Africa
“Our analyses show that there is a steady, long-term decline of megaherbivore diversity beginning around 4.6 million years ago. This extinction process kicks in over a million years before the very earliest evidence for human ancestors making tools or butchering animal carcasses and well before the appearance of any hominin species realistically capable of hunting them, like Homo erectus,” explained Faith.
Accordingly, ancient humans are not to be blamed for the extinction of large mammals in Africa. However, the researchers consider that the expansion of grasslands caused the mammal extinctions.
“The key factor in the Plio-Pleistocene megaherbivore decline seems to be the expansion of grasslands, which is likely related to a global drop in atmospheric CO2 over the last five million years. Low CO2 levels favor tropical grasses over trees, and as a consequence savannas became less woody and more open through time. We know that many of the extinct megaherbivores fed on woody vegetation, so they seem to disappear alongside their food source,” said John Rowan from the University of Massachusetts Amherst.
With over seven years of experience in online journalism, Vadim is passionate about everything related to science and the environment. For us, he will thus cover climate, environment, and science news, among others.