A dramatic change in climate that occurred about 30 million years ago resulted in a mass extinction in Africa and the Arabian Peninsula that is just now being documented by the scientific community.
A team of international scientists analyzed a large collection of fossils from five mammal groups that once roamed those regions, revealing that 63 percent of the species vanished from the Earth.
The mammal groups include a group of extinct carnivores called hyaenodonts, two rodent groups, the anomalures (scaly-tail squirrels) and the hystricognaths (a group that includes porcupines and naked mole rats), and two primate groups, the strepsirrhines (lemurs and lorises) and our very own ancestors, the anthropoids (apes and monkeys).
The mass extinction was caused when the swamp landed transformed into an icy world and followed the transition between the geological periods called the Eocene and Oligocene.
In a statement issued on Thursday, the scientists explained that ‘Earth grew cooler, ice sheets expanded, sea levels dropped, forests started changing to grasslands, and carbon dioxide became scarce.’
The period ended with nearly two-thirds of known species in Europe and Asia going extinct, but it was long believed the event spared those Africa.
The speculation was due to the region’s mild climate and closeness to the equator, but the new analysis reveals that was far from the case.
A team of international scientists led by Duke University analyzed a large collection of fossils from five mammal groups, revealing that 63 percent of the species in those regions vanished from the Earth
Using data from hundreds of fossils uncovered in Africa, the team built evolutionary trees for the five mammal groups.
This allowed them to see new lineages that branched out and determine dates for each species’ first and last known appearances.
‘It was a real reset button,’ said Dorien de Vries, a postdoctoral researcher at the University of Salford and lead author of the paper.
The team found the groups reappeared a few million years later, but had evolved with ‘a new look’ that suggests there was a recovery period following the extinction.
The mass extinction was caused when the swamp landed transformed into an icy world and followed the transition between the geological periods called the Eocene and Oligocene. The mammal groups include a group of extinct carnivores called hyaenodonts (pictured)
The greatest evidence of this was they found teeth of the animals that popped up again.
Researchers looked at animals’ fossilized molars, teeth that shed light into the creatures, specifically what they ate.
The animals that reappeared later had different diets and behaviors than their ancestors that vanished in the mass extinction, according to the study published in Communications Biology.
‘Extinction is interesting in that way,’ said Matt Borths, curator of Duke University’s DLCDFP and coauthor of the paper.
‘It kills things, but it also opens up new ecological opportunities for the lineages that survive into this new world.’
This decline in diversity followed by a recovery confirms that the Eocene-Oligocene boundary acted as an evolutionary bottleneck: most lineages went extinct, but a few survived.
The team found the groups reappeared a few million years later, but had evolved with ‘a new look’ that suggests there was a recovery period following the extinction. And the greatest evidence of this was found teeth of the animals that popped up again. Pictured is a lower molar of a fossil anomaluroid rodent
Over the next several millions of years, these surviving lines diversified.
‘In our anthropoid ancestors, diversity bottoms out to almost nothing around 30 million years ago, leaving them with a single tooth type,’ said Erik R. Seiffert, Professor and Chair of the Department of Integrative Anatomical Sciences at the Keck School of Medicine of the University of Southern California and senior coauthor of the paper.
‘That ancestral tooth shape determined what was possible in terms of later dietary diversification.’
‘There’s an interesting story about the role of that bottleneck in our own early evolutionary history,’ said Seiffert.
‘We came pretty close to never existing, if our monkey-like ancestors had gone extinct 30 million years ago. Luckily they didn’t.’
EARTH HAS HAD FIVE GREAT EXTINCTION EVENTS WITH THE MOST FAMOUS A DINOSAUR KILLING ASTEROID
Five times, a vast majority of the world’s life has been snuffed out in what have been called mass extinctions.
End-Ordovician mass extinction
The first of the traditional big five extinction events, around 540 million years ago, was probably the second most severe. Virtually all life was in the sea at the time and around 85% of these species vanished.
Late Devonian mass extinction
About 375-359 million years ago, major environmental changes caused a drawn-out extinction event that wiped out major fish groups and stopped new coral reefs forming for 100 million years.
Five times, a vast majority of the world’s life has been snuffed out in what have been called mass extinctions. The most famous may be the End-Cretaceous, which wiped out the dinosaurs. Artist’s impression
End-Permian mass extinction (the Great Dying)
The largest extinction event and the one that affected the Earth’s ecology most profoundly took place 252 million years ago. As much as 97% of species that leave a fossil record disappeared forever.
End-Triassic mass extinction
Dinosaurs first appeared in the Early Triassic, but large amphibians and mammal-like reptiles were the dominant land animals. The rapid mass extinction that occurred 201 million years ago changed that.
End-Cretaceous mass extinction
An asteroid slammed down on Earth 66 million years ago, and is often blamed for ending the reign of the dinosaurs.