A mass extinction that no one had identified until now .
Compiling decades of work, a new study of the fossils in the Duke collection by an international team of scientists has led to the discovery of a previously unknown mass extinction event in Africa. The event followed the transition between the geological periods called Eocene and Oligocene, a stage marked by dramatic climate change.
Thus, as if it were an inverse image of our present, the Earth cooled, the ice sheets expanded, the sea level dropped, forests began to turn into desert grasslands and carbon dioxide became scarce. Almost two-thirds of the known species in Europe and Asia at that time were extinct.
A dramatic change in the weather
63% of the species disappeared. Groups of extinct mammals include a group of carnivores called the hyaenodonts, two groups of rodents, the scale-tailed squirrels and the hystricognaths (a group that includes porcupines and naked mole rats), and two groups of primates, the strepsirrhines (lemurs and lorises. ) and our own ancestors, the anthropoids (apes and monkeys).
It had previously been thought that the mild African climate and proximity to the equator would have saved them, but new analysis reveals that this was far from a reality. We believed that the biodiversity of Africa had not gone badly off as, for example, it happened in the Asian continent. But we weren’t looking at the fossil record in the right way.
Of course, the ecological niches that were left open by the extinction event were not empty for long.
“It’s very clear that there was a big extinction event and then a recovery period,” said Duke University biologist Steven Heritage in his study published in the journal Communications Biology.
Although the evidence shows new tooth forms and new adaptations in animals. “It was a real reset button. After a few million years, these groups begin to appear again in the fossil record, but with a new appearance ”, clarifies Dorien de Vries, leader of the work. “The fossil species that reappear later in the Oligocene, after the great extinction event, are not the same as those found before.”
Rodents and primates that reappeared after a few million years had different teeth . They were new species, eating different things and having different habitats.
“We see a huge loss in tooth diversity and then a recovery period with new tooth shapes and new adaptations,” says Vries.
Our own primate ancestors seem to be among the most affected. Diversity in anthropoid teeth 30 million years ago was reduced to practically zero. Only one type of tooth morphology remained, limiting the types of foods their descendants could eat. And, in a way, that tooth design helped us, as our species made its way into this new setting as well.
“Extinction is interesting in that sense. It kills things, but it also opens up new ecological opportunities for the lineages that survive in this new world, ”continues Matt Borths, curator of the Duke Lemur Center Museum of Natural History where the fossils are found.
Referencia: D. de Vries et al. 2021. Widespread loss of mammalian lineage and dietary diversity in the early Oligocene of Afro-Arabia. Commun Biol 4, 1172; doi: 10.1038/s42003-021-02707-9
