2021-10-10

Fossils collected by Duke University have discovered the previously unknown African extinction

By yqqlm yqqlm

Fossils collected by Duke University have discovered the previously unknown African extinction

that period was characterized by dramatic climate change. In an image contrary to what is happening today, the earth becomes colder, ice sheets expand, sea levels fall, forests begin to turn into grasslands, and carbon dioxide becomes scarce. At that time, nearly two-thirds of the known species in Europe and Asia were extinct

African mammals are considered likely to escape unharmed. Africa’s mild climate and proximity to the equator may have been a buffer against the worst cooling trend of that period

Fossils collected by Duke University have discovered the previously unknown African extinction(1)

dental CT scans showed that mammalian teeth became less diverse during the early Oligocene extinction. Here is an example of the three-dimensional tooth shape of a fossil abnormal rodent lower molar

now, thanks largely to the large number of fossils collected by the primate fossil division of Duke University lemur Center (dlcdfp), researchers have shown that although the environment in Africa is relatively mild, African mammals are affected as much as mammals in Europe and Asia. These collections are the lifelong work of the late Elwyn Simons of Duke University, who has been searching for fossils in the desert of Egypt for decades

the team, composed of researchers from the United States, Britain and Egypt, studied the fossils of five mammalian groups. A group of extinct predators called hyaenodonts; Two groups of rodents, anomalures (scale tailed squirrel) and hystricognaths (one group includes porcupine and naked mole); And two groups of primates, strepsirrhines (lemurs and lizards) and our own ancestors, anthropoids (apes and monkeys)

by collecting data from hundreds of fossils from multiple locations in Africa, the team can establish an evolutionary tree for these groups, accurately point out when new strains branched out, and time mark the first and last appearance of each species

their results show that all five mammalian populations suffered huge losses near the Eocene Holocene boundary

dorien de Vries, a postdoctoral researcher at Salford University and the main author of the paper, said: “this is a real reset button.” millions of years later, these groups began to appear in the fossil record, but took on a new look. Later, in the Oligocene, after the mass extinction, the fossil species that reappeared were different from those found before

Steven heritage, a researcher and digital preparer of dlcdfp at Duke University and co-author of the paper, said: “It is very clear that there is a huge extinction event and then a recovery period. The evidence is on the teeth of these animals. Molars can explain what mammals eat, which in turn explains their environment. Rodents and primates that reappear millions of years later have different teeth. These are new species. They eat different things and have different habitats. We see a huge loss of tooth diversity, followed by a recovery period, with new tooth shapes and new adaptations. ”

Matt borths, curator of dlcdfp at Duke University and co-author of the paper, said:” extinction is very interesting from this perspective. “It killed some things, but it also opened up new ecological opportunities for those strains that survived in this new world.”

the decline and restoration of diversity confirmed that the Eocene Holocene boundary played an evolutionary bottleneck: most strains were extinct, but a few strains survived. Over the next few million years, these surviving strains diversified

Erik R. Seiffert, professor and chairman of the Department of comprehensive anatomy at the Keck School of medicine at the University of Southern California, said: “among our ape ancestors, diversity reached its lowest point 30 million years ago, almost zero, leaving only one tooth type.” he is a former graduate student of Simmons and a senior co-author of the paper. “The shape of this ancestor’s teeth determined the possibility of dietary diversification later.”

“there is an interesting story about the role of that bottleneck in our own early evolutionary history,” Seiffert said. “If our ancestors like monkeys died out 30 million years ago, we would probably never exist. Fortunately, they did not.”

the rapidly changing climate is not the only challenge for these few surviving mammal types. As the temperature dropped, East Africa was impacted by a series of major geological events, such as volcanic supereruption and proluvial basalt – huge eruption covered large areas of lava. It was also at that time that the Arabian Peninsula separated from East Africa, opening up the Red Sea and the Gulf of Aden

borths said: “at the Eocene Holocene boundary, we lost a lot of diversity. But the surviving species obviously have enough toolbox to survive this fluctuating climate.”

Hesham sallam, founder of the vertebrate paleontology center at mansura University in Egypt and co-author of the paper, said: “Climate change in the geological period has shaped the evolutionary tree of life. Collecting past evidence is the easiest way to understand how climate change will affect ecosystems