By Will Dunham
(Reuters) – More than 250 million years ago, Scotland was not shrouded in fog and rain as it often is today, but rather a desert covered in sand dunes. One of the denizens of this harsh landscape was a stocky, dimly porcine ancestor of a mammal named Gordonia, with a pug face and two tusks protruding from beaked jaws.
Using a high-resolution three-dimensional view of this Permian period fossil, scientists were able to see its brain cavity and create a digital replica of the brain, providing insight into the size and composition of this key organ at an early age. stage of mammalian evolution.
To be clear, Gordonia’s brain was far from that of a modern mammal. However, 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—an ancestor of mammals that still retained features of reptilian ancestors.
“Overall, Gordonia’s brain looks more reptilian than mammalian, despite being more closely related to us than to any modern living reptile,” said University of Bristol palaeontology PhD student Hady George, lead author of the study published this week in the Zoological Journal of the Linnean Society.
The front part of Gordonia’s brain — the forebrain — is proportionally much smaller than that of any mammal, George said. While Gordonia’s brain is generally typical of an ancient mammal relative, an organ called the pineal gland, which is dedicated to metabolic functions, was greatly expanded, George added.
But there seem to be some early glimpses of what was to come.
“What we see is a brain that looks very different from ours, it’s not a big ball like a balloon, but rather a long, arched tube. But even though its shape looks strange, when we measure its volume, we can see that it was quite large compared to body size,” said paleontologist and lead study author Steve Brusatte of the University of Edinburgh.
“It’s so hard to measure intelligence in modern animals, and even more so in long-extinct species that we can never directly observe. But we can at least say in general that it would have been a smart creature for its time. The increasing size of its brain compared to other animals of that era, we can feel the early evolutionary roots of our own huge brains,” added Brusatte.
Gordonia was about three feet (one meter) long and weighed approximately 45 pounds. His head was tall and broad. Although he had a squat and a pig’s body, his legs were not as long as a pig’s.
“The combination of beak and tusks allowed for a herbivorous lifestyle, and in particular for plucking succulent roots from the desert it created,” George said.
It was a species of protozoan called a dicynodont that 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 – thought to have been caused by massive volcanic activity in Siberia – although Gordonia did not.
It was as a result of this catastrophe that the first dinosaurs appeared about 230 million years ago. Mammals subsequently appeared about 210 million years ago, scrambling under the feet of the dinosaurs. Only after an asteroid strike 66 million years ago wiped out the competition did mammals get a chance to dominate.
The Gordonia fossil, discovered in 1997, is a sandstone block containing a void perfectly enclosing the skull and lower jaw.
“The Gordonia brain bears very little resemblance to the brains of modern mammals and has none of the unique features that characterize mammalian brains. This shows how much the brain had to change to become what we would recognize as a true mammal today,” George said.
(Reporting by Will Dunham in Washington; Editing by Daniel Wallis)