Scientists Discover Something Amazing about the Brain Evolution of Mammals

Scientists Discover Something Amazing about the Brain Evolution of Mammals

A study at the University of Texas reveals that the mammals traded their reproduction capabilities in order to have a bigger brain.

Fossils are extremely vital when it comes to revealing the secrets of the past. They guide the paleontologists of our age about the happenings that took place millions of years ago. Consequently, it gives them a better understanding of the life during those times. Recently, researchers from the University of Texas found fossils of a mammal forerunner which provided outstanding insights into the brain evolution of mammals. It reproduced like reptiles and the fossils of her 38 babies were also traced alongside the mother which led scientists to the conclusion that mammals traded their reproduction abilities for brain power. They regarded this finding as a key development in the evolution of this class of the animal kingdom.

The researchers who took part in this study mentioned that this finding is the rarest of the rare because the only known fossils of babies from any mammal precursor were located in this research. The number of these babies is the thing that surprised the paleontologists as it was more than twice the average litter size of any living mammal. This gave them the idea that the reproduction of mammals was quite similar to reptiles in the ancient times. Eva Hoffman, a Graduate Student at the UT Jackson School of Geosciences who led this research, talked about the importance of this finding and said,

These babies are from a really important point in the evolutionary tree. They had a lot of features similar to modern mammals, features that are relevant in understanding mammalian evolution.”

Timothy Rowe, the graduate advisor of Hoffman who Co-authored the study, was the one who collected these fossils from a rock formation in Arizona some 18 years ago. At that time, he had no idea that there were so many babies in there as he thought he was bringing home a single specimen. Sebastian Egberts, a former Fossil Preparator at the Jackson School, was the first person to see a sign of babies in the fossil. He observed a grain-sized speck of tooth enamel while unpacking the fossil in 2009. He described his experience in the following words:

It didn’t look like a pointy fish tooth or a small tooth from a primitive reptile. It looked more like a molariform tooth (molar-like tooth) — and that got me very excited.”

The initial CT scan of the fossil only showed a handful of bones inside the rock but the advancements in the CT-imaging technology, over the next 18 years, led to this amazing discovery. Hoffman complemented the expertise of the technicians at the High-Resolution X-ray Computed Tomography Facility at the University of Texas with her Digital Processing skills to come up with complete skulls and partial skeletons. It was found that the mammal relative belonged to ‘Kayentatherium Wellesi’, an extinct species of beagle-size plant-eaters. These creatures roamed across the Earth, alongside dinosaurs, about 185 million years ago.

Hoffman based her analysis on the 3D visualizations and observed that the tiny bones belonged to the same species as the adult. Similarly, she found that the skulls of the babies were proportional to the adult’s, despite being 10 times smaller in size. This is a complete contrast with respect to mammals whose babies are born with spherical heads and shortened faces to incorporate big brains. The fact that Kayentatherium had a tiny brain and quite a lot of babies hint towards a ‘Mammalian Evolution’ where big litters were traded for bigger, more powerful brains. Rowe referred to that in the study by saying,

“Just a few million years later, in mammals, they unquestionably had big brains, and they unquestionably had a small litter size.”  

Pregnancy is an energy-intensive process and the mammalian reproduction is directly relatable with human development including the growth of the brain. Rowe added that studying the early mammalian ancestors can prove extremely helpful in understanding the evolutionary procedures that made us what we are today as a species. Talking about the potential of studying the evolution of mammals in the future, he said,

There are additional deep stories on the evolution of development, and the evolution of mammalian intelligence and behavior and physiology that can be squeezed out of a remarkable fossil like this now that we have the technology to study it.”

Computer Scientist by qualification who loves to read, write, eat, and travel

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