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Big Brains, Average Smarts?

We humans tend to pat ourselves on the back for the contents stored within our skulls. Indeed, our big brains and unique intelligence push us to the top of the food chain and set us apart from other species in the animal kingdom.

To a certain point, it is true. The size of our brains gradually increased starting six million years ago, the point in time scientists generally agree upon as to when humans and apes’ evolutionary paths diverged. Our brains weigh in at around three pounds with an average length of 15 centimeters. In contrast, chimpanzees, our closest living relatives, have brains that weigh under a pound.

Brain scans reveal humans have a high amount of "white matter," an ocean of nerve cells bouncing to and fro. Scientists employ terms like “neocortex,” “frontal lobe,” and “cerebrum” to explain our uniquely human capabilities, such as dealing in abstract concepts, complex language, collecting and storing information over long time spans.

New studies, however, serve up two sobering perspectives: 1) that our brain size isn’t so special after all; and 2) that our brain size does not necessarily explain how we got to be, well, so dang smart.

A chimpanzee brain, left, compared to a modern human brain, at right. Source: Smithsonian

An international team of researchers set out to measure the space occupying the skulls of more than 1,400 living and extinct mammalian species. The researchers then compared this data with the evolutionary trajectory of species’ body size. Bigger body means bigger brain, right?

Not necessarily. Take the sea lion, for example. Weighing in at a beefy 220 pounds, and growing up to two meters long, the marine creature has a brain the size of a chimpanzee. Yet the sea lion is no oaf. It is a quick learner and, to a certain extent, understands human communication.

Polar bears have a similar body mass to the sea lion, yet a brain twice the size. On the other side of the spectrum, measuring for scale, chihuahuas and certain species of fish have bigger brains proportional to their body than we do!

These findings appear to show that over time and across species, evolution can create bigger cavities in the skull —but is not obliged to fill them with high-functioning brains.

The uniqueness of human cognition is not due to brain size, nor to a more developed frontal cortex, but rather “distributed neural networks,” according to another study. In other words, we have mental flexibility; our brains’ different regions talk to each other more often than other animals.

Thousands of years ago, our ancestors did not invent fire, blades and bone tools, and later agriculture, due to a new brain structure. They simply implemented a “better use of the structures we already had through the very gradual acquisition of the ability to switch between modes of thought depending on the context.”

Of course, this ability to navigate the waves of “context” and “thought modes” throughout our evolution does not occur in isolation as some abstract notion, as it appears here in writing. As scientists Liane Gabora and Scott Barry Kaufman argue in The Cambridge Handbook for Creativity:

The creative process is compelling and our creative achievements unfold with breathtaking speed and complexity in part because we are fortunate enough to live in a world that offers infinite possibilities for exploring not just the realm of “what is” but the realm of “what could be.”

Who holds the keys to the realm of “what could be?” One could say “the individual human mind.” But the more likely answer is other minds: those of our friends, our families, our peers, our ancestors. And for that, we can pat ourselves on the back.






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