Do Big Brains Make Us Smart?

The Answer is No



Humans have the largest brain-to-body ratio of any animal. We have giant, complicated, brains that should make us the smartest animals on  Earth. But oddly, we spend so much of our time trying to dull that intelligence—we drink alcohol, take drugs, go shopping, have sex, watch TV, look at our phones for hours, read, talk to each other a lot, and spend most of the day with useless thoughts wandering through all those brain cells.


In other words, we have big brains but can’t handle them. It’s like we were handed a Ferrari to drive through life but decided to walk instead.


The human lineage, called Hominids, appeared about 6 million years ago. These ancestors walked upright like modern humans but had brains the size of apes, about 400 cubic centimeters. Over the next many millennia that ape brain filled out to about 1400 cc’s. It’s clear that Natural Selection was favoring this increase in brain size because brain tissue takes an excessive number of calories to support.


But no one knows why this spectacular brain growth in the human lineage was advantageous. Some have suggested tool use as a driver, but human brains began to get bigger way before there is evidence of tools in the fossil record. Some cite spoken language as the reason for large brain size, but language came really late to humans, far past the time when we had already achieved our current cubic centimeters of brain tissue. Maybe it was a response to changing climates and the concomitant need to seek out food and water under differing environmental conditions. One anthropologist has even suggested that cooked food was the trigger since that provided more protein in the human diet which meant more support for more brain cells.


My favorite hypothesis focuses on humans as social animals and the need to keep track of complex social relationships that were helpful for survival. Bigger brains, bigger address books, more friends and alliances when the going gets tough. And this hypotheses gains credence because inter-personal connection acts as critical social shield. Most primates, such as us, are social animals and they rely on each other for survival, so connecting up is imprinted on our genes just as it is in other animals. And so, being part of a group—family, religion, ethnicity, political party, hobby, whatever—is part of our identity, and being alone is both awful and detrimental to our physical and mental health.


But if sociality is why we have big brains, we’ve botched that too. In developed countries, the marriage of capitalism and its evil twin, the underlying tenent to “make it on your own,” is the exact opposite of forming protective groups. This mismatch was brilliantly clear during the Covid pandemic, explicitly in America, land of lauded self-sufficiency and self-importance. What smart social animal refuses a vaccine against a deadly virus and doesn’t give a fig that they might pass it on to others? Is this large-brained person smart when they don’t listen, refuse vaccines, and put others in their community at risk for illness and death? Are they smart because they infuse the word “freedom,” meaning personal freedom, into public health which protects us all? It is no surprise that America, with only 4% of the world’s population has had 17% of the Covid deaths worldwide. Just plain stupid.


Along with this so-called intelligence (let’s call it puzzle-solving skills), also came the ill-defined abilities known as consciousness and self-consciousness. That is, we know who we are, have memories of the past, and fantasize about the future, and we have a “theory of mind” which means “I know that you know” about other people.


But big brains and consciousness are false gods. In fact, they don’t always work well; our brains make tons of misinterpretations all day long, and often can’t puzzle their way out of a paper bag. And there is wide variability in every single measure of intelligence (It’s amazing how many stupid humans there are). And yet, we continue to view our brain size and intelligence in a very self-serving way. We hold up our smarts and consciousness as some kind of medal won in the game of evolution and then declare that this “achievement” gives us rights to the rest of the planet. But if we are the “natural” and “intelligent” stewards of the plant, then we are doing a really bad job at it, and our brain size is no advantage.


As a species, we seem to be bumbling and fumbling about, destroying our environment, as well as each other. Are these the actions of a smart evolutionary successful species? No. Of course not.


For decades, I taught Human Evolution to 20-year-olds. I showed them our tiny-brained ancestors and the path of brain growth to modern humans. For many, this information was confirmation that humans are at the “top” of the evolutionary scale (let’s celebrate!) and that gave them license to do whatever they wanted. But for the smarter students, it gave them pause for thought, especially during raves, frat parties, being sick with the flu, and when the sky turns orange.