Closing out an evolutionary trifecta for May. Our ramshackle remodeling has brought us a big, beautiful brain, but is it really the size that gives us our smarts? If overall mass were all that mattered, you’d have to open an underwater chapter of MENSA, as the sperm whale’s brain swells past all others at nearly 20 pounds. Ours, by comparison, is only about 3 pounds. It should be obvious, though, that absolute size can’t be the dominant indicator, as a lot of that real estate is needed just to communicate with a body that big.
That’s why a better rule is the ratio of brain size to body size. We start to sit a lot prettier from that viewpoint, as primates boast brains 5 to 10 times larger than the “average” animal proportion. Then again, a person’s brain size to body size ratio is just about the same as that of a mouse. Birds and ants actually come out ahead of us. There must be something else yet still at play.
Is it how the organ is organized? A March study from Jeroen Smaers and Christophe Soligo of the University College of London seems to show, through analysis of 17 primate species that span 40 million years of evolutionary history, that we really started to take off with an accelerated growth of a specific region of the brain, namely the prefrontal cortex. The prefrontal cortex, part of the frontal lobe, is accepted to be where our thoughtful “executive functions” take place. In other words, the bit that makes us human.
Three pounds of goo that makes you you. From scientificamerican.com
Hold on a second, say Robert Barton and Chris Vendetti in an even more recent study! With their data they counter that, contrary to popular wisdom, the size of our frontal lobes isn’t any bigger than what you’d expect for our bodies. They argue that previous investigations didn’t tackle the “scaling” issue properly. Instead, the pair propose we take a closer look at our heightened connectivity between different brain areas.
WHAT DOES THIS MEAN?
What was once “common sense,” that a big brain makes for a brighter being, hasn’t been taken seriously for a while, and even the ideas that supplanted it, like size ratios and organizational complexity, have come under criticism. We’re not lacking for new ideas on the subject, as British researchers Seth Grant and Richard Emes once presented yet another alternative hypothesis, that it’s the number of different protein interactions in our synapses that set us apart from the rest.
It goes to show just how knotty the study of intelligence can be. What seems obvious isn’t always true and each successive assertion needs to scrutinized by the community. New ideas are always cropping up and should be considered. Our thoughts have gotten us far, but how we got them is still not completely certain.