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Cerebellum Growth Explosion Made Man From Monkey

Oct 03, 2014 01:05 PM EDT

A team of researchers are arguing that the cerebellum, not the neocortex, is the "seat of all humanity" and what truly helped us become more than apes millions of years ago. Such a theory goes entirely against traditional neuroscience and evolutionary theories, but according to a recent study, the team has some strong evidence to back their claim.

The study, recently published in the journal Current Biology, details how the cerebellum grew much faster than the neocortex in our ape ancestors, suggesting it was this part of the brain that first prompted some distinctly human behaviors and thoughts.

Rob Barton of Durham University and Chris Venditti, of the University of Reading in the United Kingdom, recently took a very close look at what experts believe the brains of our distant ape and monkey ancestors were like. During the evolution of monkeys, the neocortex and cerebellum grew in tandem, as one tends to complement the other.

For instance, neuroscientists know that both parts of the brain are likely involved with motor control and language. The neocortex is also involved in higher function such a sensory perception, spatial reasoning, and even conscious thought - which is what led theorists to believe that it was what truly made man. However, the cerebellum is likewise involved in some pretty important stuff. Many experts believe that the cerebellum controls factors that are more difficult to understand, such as fear and pleasure regulation, attention, and even motor learning.

According to the researchers, starting with the first apes around 25 million years ago and through to chimpanzees and humans, the cerebellum suddenly was growing much faster than the neocortex.

"That's not to say the neocortex is boring," Barton told New Scientist. But, "the difference in ape cerebellar volume, relative to a scaled monkey brain, is equal to 16 billion extra neurons. That's the number of neurons in the entire human neocortex."

He argues such rapid growth must have happened for a reason.

However, not everyone is convinced. Susanne Shultz, an expert on the evolution of behavior, argues that it simply could have been that the cerebellum had to spike in growth in order to coordinate all the radically "human" and complex behaviors that a changed neocortex had already sparked.

If she's right, that would certainly the be a "reason," just not the one Barton was hoping for.

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