Ancient Rodent Had Large Brain, But Wasn't Necessarily 'Smart'

Is a bigger brain better? Researchers from the University of Toronto are shedding new light on the brain evolution in early rodents. These researchers conducted an in-depth study where they examined the brains of an ancient rodent that lived during the mid-Eocene period, 47 to 50 million years ago. The study indicates that brain size is not the only indicator of intelligence. It turns out bigger doesn't mean better, after all!

The researchers reconstructed two endocasts of Paramys, which are oldest and best-preserved rodent skulls on record. Paramys' neocortex region (area that deals with "higher" brain functions like sight and hearing) is smaller than most primitive primates, according to the researchers.

"The brain was certainly larger than we expected considering the time period," Ornella Bertrand, coauthor of the study, said in a news release. "Even more surprising is that it was almost as large, and in some cases larger, than primitive primates of the same time period."

The researchers found that primate brains were not always exceptionally large, but they were "smart." One of the ancient rodent samples was three kilograms, which is about the size of a small cat, this rodent lived 47 to 49 million years ago. The other rodent was had a body mass of about one kilogram and lived 50 to 52 million years ago.

"Size is certainly important, but we're starting to look at different measures that give us a more nuanced understanding of how brains, especially in primates, evolved over time," said Mary Silcox, coauthor of the study.

The findings of this study were published in the Proceedings of the Royal Society B.

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