Scientists have recently discovered the existence of what they call the “lost extinction”, a phenomenon that took place in Africa. This event began 34 million years ago and wiped out most of the primates and rodents. The carnivores that preyed on these animals also gradually disappeared. Until now, scientists did not suspect the existence of this phenomenon, which lasted for millions of years.
According to the information, this period of extinction occurred between two different geological epochs: the Eocene and the Oligocene. The first era began 55.8 million years ago and ended 33.9 million years ago. The second began 33.9 million years ago and ended 23 million years ago.
As the greenhouse climate of the Eocene began to change to the frosty climate of the Oligocene, sea levels dropped and the Antarctic ice became thicker. During this period, almost two-thirds of animal species in Europe and Asia became extinct. Scientists thought that African species were saved due to their proximity to the equator. But this new discovery shows that this is not the case.
Methods used by researchers
With few clues from the time, researchers weren’t sure what happened in Africa when temperatures started to drop. However, the new study looked at animal lines and found that the African continent has also been hit hard.
Scientists have reconstructed the time lines of evolution in the family trees of 5 groups of African mammals. They focused on two groups of primates, two groups of rodents, and a group of now-extinct predators known as hyanodons.
According to Eric Seiffert, professor and director of the Department of Integrative Anatomical Sciences at the University of Southern California and co-author, we don’t have the density of fossil records that other African continents have. So they had to find a way to extract as much information as possible, hence the new approach.
Scientists used the fossils they had on hand to track the diversity and extinction of species over time. The results then showed that about 34 million years ago, a drop in temperature wiped out entire branches of the family tree of the mammals in question. Species diversity has not declined drastically, as is commonly seen during global extinctions. Rather, the decline unfolded over millions of years until 63% of the species in the mammalian groups became extinct.
When the studied groups began to diversify again, most of the new species evolved to acquire new characteristics that were not there before extinction. One can cite as an example the species of primates and rodents that appeared in the Oligocene. These species had different forms of teeth than their already extinct counterparts. This shows that these species have adapted to survive in different ecosystems than their predecessors.
Thus, we know that an extinction occurred between two geological periods. As for the exact cause, some evidence found in Africa and the Arabian Peninsula 31 million years ago suggests otherwise. Active volcanoes could create an insurmountable problem for the survival of these species.