Scientists from the University of Arizona (USA) conducted a new study, comparing climate data with information about the fossil remains of large mammals that have lived in Africa over the past 4 million years. As a result, biologists have cast doubt on the long-standing hypothesis that repeated climate changes were the main drivers of evolutionary change in mammals, including human ancestors.
Scientists have turned their attention to the Pliopleistocene epoch, which spans roughly the last 5 million years and includes the last ice age about 20,000 years ago. At this time, there was a change in the orbit and orientation of the Earth relative to the Sun. The planet was exposed to solar radiation of varying intensity, which led to climate change.
The idea that climate change may have been the driving force behind human evolution goes back to the time of Charles Darwin. As human ancestors faced rapidly changing conditions, they must have become resourceful and able to cope with many different contingencies. And this led to the emergence of new species, while others died out.
In the new study, experts analyzed samples taken from sediments from lake beds, the ocean floor and land excavations from 17 sites across the African continent. The climatic data were then directly compared with the fossil record of large mammals—primarily cattle, a family that includes antelopes and other large herbivores. The researchers focused on these animals in the first place because the fossils of human ancestors are too rare – there are far fewer of them.
“If climate variability is an important driver of evolution, it should also be a driver of the evolution of other large mammals,” the researchers said. They noted that in general, over the past 3.5 million years, there has been a long-term trend towards increasing environmental variability. And all the while, the fossil record of the origin and extinction of species among large herbivores has been undertaking a new study, comparing climate data with information on fossils of large mammals that have lived in Africa over the past 4 million years. As a result, biologists questioned the long-standing hypothesis that repeated climate changes were the main drivers of evolutionary change in mammals, including human ancestors. Animals are not associated with climate change, writes Phys.org.
“We are not saying that environmental variability is not important for human evolution, but the data we have currently collected is very inconsistent with this idea,” the experts explained.