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Mammals are the brains of the animal world. brain of your brain sperm whale At 20 pounds it is the largest brain in the world, and your three-pound brain is seven times the size of what would be expected of an average human body. Collectively, mammals have the largest brain to body size ratio among vertebrates, a fact that helps explain their cognitive abilities. Larger brains are generally better at coordinating complex behaviors, solving puzzles, and responding to environmental change.
But a study published Thursday, journal Science turns out that mammals weren’t always this bright. During the Paleocene, a chaotic chapter of Earth’s history, The asteroid impact that decimated the dinosaurs 66 million years ago, our ancestors seem to prioritize muscles over brains. But it may have been the clever evolutionary strategy of the time that gave animals the strength to survive and thrive in a harsh environment.
A team of paleontologists used CT scans to examine the inside of fossilized skulls recently unearthed in New Mexico and New Mexico to watch how brain sizes fluctuate. Colorado.
“Paleocene mammals are very strange,” said Ornella Bertrand, a postdoctoral researcher at the University of Edinburgh and author of the study.
These include Arctocyon primaevus, a toothed predator that resembles a hyena but is actually most closely related to modern sheep and pigs; and Hyrachyus modetus, a stocky relative of rhinos and tapirs from the later Eocene Period.
These strange mammals weren’t particularly intelligent. The researchers used CT scans to measure brain envelopes and compared them to the expected brain size and evolutionary history for an animal this size. They found that during the Paleocene, mammals’ relative brain sizes actually decreased, challenging the long-held assumption that mammals always had relatively large brains.
But that only tells half the story, because the brains themselves were not shrinking. Instead, mammals were getting much larger in the post-dinosaur era. While many acted like balloons to save dimensions, their brains struggled to keep up.
This spurt of growth occurred millions of years ago. When dinosaurs dominated terrestrial ecosystems, the largest mammals were the size of a badger. Although diverse, these pint-sized mammals burrowed underground, perched high in trees and writhing under their feet.
But once the smoldering fallout from the asteroid impact is cleared, these ecological bit actors took the stage.
“They had to navigate a destroyed world,” said Stephen Brusatte, a paleontologist at the University of Edinburgh and author of the study. “These were animals that literally took over from the dinosaurs, moving into niches once occupied by Triceratops and raptor dinosaurs.”
With the extinction of non-avian dinosaurs, mammals had full access to a leafy buffet and began to eat en masse. But as it grew rapidly, the size of the brains in the growing skulls gradually increased.
Xiaoming Wang, a paleontologist at the Los Angeles County Museum of Natural History, said this trend of the mass on intelligence makes sense because a large, specialized brain doesn’t come cheap.
Not involved in the new study, Dr. “Our brain is like a supercomputer and it consumes a large amount of energy,” Wang said. “So the idea is that you don’t increase the size of the brain unless absolutely necessary.”
And it seems that after extinction, a big brain wasn’t worth the cost. These ancient mammals, though likely dimmer than their modern counterparts, dominated the recovering ecosystems.
However, the reign of retarded mammals would not last. In the subsequent Eocene Period, about 10 million years after the asteroid impact, ecosystems were swarming with large mammals. Resources were no longer readily available, meaning creatures had to be smart to avoid overeating or being eaten, and smarter mammals could outpace their smaller-brained brethren.
Although overall brain size has increased since then, not all larger brains are created equal. Dr. Bertrand and colleagues found that as competition intensified during the Eocene, the brains of some mammals became more specialized, growing in areas involved in vision, balance and eye movement.
Mammals with well-developed brains also had ancestors that gave rise to modern horses, whales, bats, and eventually Homo sapiens.
Dr. “There is definitely something special about our ancestors,” Bertrand said.
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