It has taken over two decades and one pandemic for paleontologists to unite the fossils of the earliest mammal ancestors and find that their evolution which gave rise to modern humans may have begun in the southern hemisphere.
Our understanding of when and where modern mammals evolved on their heads was changed by the analysis of a small collection of fossils.
Thomas Rich is a long time fossil hunter.
In 1997, after 23 years of searching, he was part of the team that announced they had found a mammal jawbone with strange teeth on a beach in Australia. The bones were from a small shrew-like creature that lived in the middle of the last century.
In the years that followed, more mammal jawbones were discovered, most recently in Australia.
The back teeth of each specimen were unique. The oldest fossil in the Northern Hemisphere is 50 million years old.
Our theory of mammal evolution has been completely altered by these discoveries. Rich says that it turns our idea of mammal evolution on its head.
The teensy teeth in question interlock top and bottom to cut, crush, puncture and grind plant food.
The three Australian tribosphenic mammal fossils, the most recent of which was described in 2020 by the Australian Museum's chief scientist, were the subject of an idea to revisit by Tim and Kris.
The Argentinean specimen is millions of years older than any other early mammal fossils found in the north.
They mapped out an alternate origin story for mammals, whose ancestors could have traveled between the southern and northern hemispheres 125 million years ago.
Based on the age of the fossils and their similarities, the team believes they are the earliest ancestors of the koalas and wombats in Australia.
According to Heglen's research, Theria flourished in Gondwana for 50 million years before moving to Asia. They diversified quickly after arriving in Asia.
The specialized molars of our earliest mammals may have been the key to their success. The evolution of early mammals who outlived the dinosaurs has fascinated scientists for many years.
The weight of evidence is very important in paleontology. The abundance of fossils found in the Northern Hemisphere and the diversity of mammals there led scientists to believe that the ancestors of placentals and marsupials arose in the north.
Fossil records can be skewed by who is looking where. It has taken several decades to find even the seven small teeth that were thought to be the first mammals.
It's the most important piece of research I've ever published, but it may take some time to find full acceptance among Northern Hemisphere researchers.
It took him a while to accept the findings. The evidence is compelling and I resisted the conclusion as long as I could.
Not every paleontologist is convinced. While Flannery and team are holding this new revelation up as a massive discovery that upends our understanding of mammal evolution, Prideaux says their conclusions are based on the smallest shards of fossil teeth.
He told the Sydney Morning Herald that it was possible that the teeth evolved in a few different places at the same time. He said the jury is out.
The study was published in an Australian journal.
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