By Will Dunham
(Reuters) – More than 250 million years ago, Scotland was not shrouded in mist and rain, as is often the case today, but rather a desert covered in sand dunes. One of the inhabitants of this challenging landscape was a stocky, vaguely pig-like forerunner named Gordonia, with a pug face and two tusks protruding from its beaked jaws.
Using high-resolution three-dimensional imaging on a fossil of this creature from the Permian period, researchers have managed to see the brain cavity and create a digital replica of the brain, providing insight into the size and composition of this crucial organ in an early stage. stage in mammalian evolution.
To be clear, Gordonia’s brain was far from that of a modern mammal. But the relative size of its brain compared to its body seemed to foreshadow the intelligence that later helped mammals – including humans – dominate the Earth.
Gordonia, which lived about 254-252 million years ago, was a type of animal called a protomammal – a predecessor of mammals that still retained the features of reptilian ancestors.
“Overall, the brain of Gordonia is more reptile-like than mammal-like, despite being more closely related to us than to any modern living reptile,” says palaeontology PhD candidate Hady George from the University of Bristol, lead author of the study published this week in The Guardian magazine. the zoological journal of the Linnean Society.
The front of Gordonia’s brain – the forebrain – is proportionately much smaller than that of any mammal, George said. Although Gordonia’s brain is generally typical of an ancient relative, an organ called the pineal body, which dealt with metabolic functions, was very enlarged, George added.
But there already seem to be some early signs of what’s to come.
‘What we see is a brain that looks very different from ours, not a big balloon-like sphere, but more of a long, curved tube. But even though the shape looks strange, if we measure the volume we can see that it is quite large compared to the size of the body,” says paleontologist and lead author of the study Steve Brusatte from the University of Edinburgh.
‘It’s so difficult to measure the intelligence of modern animals, and even more so in long-extinct species that we can never observe directly. But at least we can say in general that it would have been a smart creature for its time. The increasing size of its brain compared to those of other animals of the time allows us to sense the early evolutionary roots of our own enormous brains,” Brusatte added.
Gordonia was about three feet tall and weighed about 45 pounds. His head was long and broad. Although it had a stocky and pig-like build, its legs were not as long as a pig’s.
“The combination of beak and tusks allowed for a herbivorous lifestyle, especially plucking juicy roots from the desert that made it home,” George said.
It was a type of protomammal called a dicynodont, which first appeared about 265 million years ago and became extinct about 200 million years ago. As a group, dicynodonts survived the worst mass extinction in Earth’s history, 252 million years ago, at the end of the Permian – believed to be caused by immense volcanic activity in Siberia – but Gordonia did not.
It was in the aftermath of that disaster that the first dinosaurs appeared about 230 million years ago. Mammals next appeared about 210 million years ago, when they scurried under the feet of the dinosaurs. Only after an asteroid impact wiped out the competition 66 million years ago did the mammals have a chance to dominate.
The Gordonia fossil, discovered in 1997, is a block of sandstone containing a void that perfectly encloses the skull and lower jaw.
“The brain of Gordonia bears very little resemblance to the brain of modern mammals and does not possess any of the unique features characteristic of mammalian brains. This highlights how much more the brain had to change to become the one we see today as would recognize a real mammal,” says George. said.
(Reporting by Will Dunham in Washington; Editing by Daniel Wallis)