Are Our Brains Are Getting Smaller?

These are of course estimates because there aren’t any old brains to look at, which leaves just best guesses from endocranial cast models made of the inside of old skulls; these models provide clues about brain size, shape, and surface changes over the millennia, but some scientists believe that they can only provide limited data. 

Even with the lack of definitive proof this is still an interesting and yet rather concerning prospect to wrap our shrinking brains around, and despite technology getting smaller while making great advances may be a sign of progress losing all important grey matter really doesn’t sound too appealing. 

What does this mean, what is in store for the future, and does the smaller size mean we are becoming less intelligent? “It does not mean that we are less intelligent than our fossil ancestors,” Prof Hofman says.

Anna Henschel MSc, a final year PhD candidate at the University of Glasgow’s Social Brain In Action Laboratory, tells us that the size of the brain is not a good indicator of IQ at all. “The relationship is weakly correlational at best,” she says.

It is actually a little confusing because in the grand scheme of evolution our brains have become bigger on the whole, and have gradually grown in relation to body size from early primates to Homo sapiens. 

If bigger brains are equated to more intelligence than the likes of whales and elephants with much larger brains should be much smarter than humans, but relative brain size may be of more importance than the absolute brain size in determining factors such as intelligence and behavioural complexity. To add to the confusion, this is not always the case as humans have a relative brain to body mass of 2% which is bigger than other mammals, but the brain of say a shrew can by 10% of its entire body mass. 

Prof Hofman explains, “size isn’t the whole story’ and there is a lot more going on. It’s important to consider the brain’s neural organisation, how it works and how the neural network is organised,” he says. “In that respect, you may compare our brain with a computer: bigger does not necessarily mean more powerful or faster.” A good example, Prof Hofman tells us, is the difference in brain size between men and women. “Although females have a considerably smaller brain than males, there are no differences in intelligence between the sexes,” he says. “It simply turns out that male and female brains are differently organised.”

So it would appear as if having smaller brains may not mean a less intelligent brain, but there is no definitive answer as to why our brains are changing, at least not yet. Brain structure and organisation remains one of the great mysterious unknowns of biology, even with all the modern day advances. 

What makes the topic of brain size equally frustrating and fascinating at the same time is that many scientists and researchers have proposed many different theories over the decades that link brain size to a variety of things, including changes in climate, lack of aggression, and living in big groups, and most theories sound plausible, yet it is still up for debate without definitive answers. 

“It’s very likely related to the decline in humans’ average body size during the past 10,000 years,” Prof Hofman says. “This may be a consequence of the changes in climate, diet, predation and food availability since the last Ice Age.”

The brain size is often scaled to body size because a larger body will need a larger nervous system to make it work; basically as our bodies became smaller, so did our brains…. Maybe? 

Modern human shrinking body size could be related to the warmer conditions since the last ice age, as it is known that colder climates favour bigger bodies which are better at conserving heat, and some propose brains became smaller in response to humans becoming less aggressive and more sociable/domesticated. 

In the past we needed different skills to evade predators and hunt for food, this theory is inline with the self domestication hypothesis which posits natural selection has favoured friendly, sociable, less aggressive, more helpful humans and our brains changed as a result. 

Numerous studies have found this to be true in animals that live in the wild as compared to similar domesticated animals such as wild wolves tending to have larger brains and are better at existing without human help, while dogs have smaller brains and perform higher on testing for social intelligence and have learned to live alongside humans. 

This brings us to the idiocracy theory, which is in reference to the movie about an average man being put into hibernation and wakes up 500 years later to find he is now the smartest man on the planet because everyone is substantially less intelligent while technology has advanced. Some cognitive experts argue that as society has become more complex and advanced our brains are getting smaller because humans don’t need to be as intelligent to survive, and they can rely on others.

This theory suggests that our brains are smaller because we are dumber than our ancestors; but this would also depend apon the definition of dumb, as just as the theory of domestication, our environment, lifestyle, and priorities have changed, so the brain has too.

Some studies suggest that there may be a correlation with cultural development: Much of our memory and cultural information can now be stored externally, what once was all in memory went to being stored in stories, books, and now in technology, and this has altered our brains significantly. 

This suggests that the brain isn’t becoming smaller and dumber, rather possibly smaller and more efficient. Some scientists suggest that it even makes sense for the brain to get smaller and more efficient because the cost of producing and maintaining it is high, the brain is greedy and it takes a lot of energy to keep it functioning properly. 

One study suggests brain size should be reduced through natural selection whenever the cost outweighs the benefits. Another suggests that large animals have greater numbers of neurons in their brains, but there may be a lower density of neural activity at any one time, meaning a smaller brain could mean less overall neurons but more being active to work simultaneously. 

So science is really searching everywhere to find answers and create theories as to why the brain is shrinking, but there are no clear answers, yet.  But maybe none of this matters because soon technology will be developed to fill in the gaps, maybe humans will gain the ability to enhance our brains with artificial intelligence, like in science fiction movies. 

Some may laugh off brain computer interfaces, but for better or worse, this technology is currently being developed. Such as that being developed by Elon Musk with his Neuralink which he claims will be implanted into the brain to allow humans to interact with tech around us. The Neuralink is still in its infancy, but for how long is uncertain. If such technology will be allowed to be produced it faces many ethical hurdles among many other fear provoking challenges to overcome.

“The effectiveness of these devices has recently been called into question in the scientific community,” Henschel said. “Increasing the activity in one brain area might take away activity in another brain area. The different parts of the brain don’t function in isolation.”

This is because of homeostasis which is the stability required by living systems to function; meaning the temperature, salt levels, blood sugar, and various other functions that are kept balanced by the brain and any external influence that are rapidly addressed to maintain it. 

For many the reason this topic is so altogether confusing and equally interesting is the same reason we don’t know exactly why the brain is shrinking or why experts think that tinkering about with the brain with technology might be risky… the human brain is beautiful and mysterious, there is still much we don’t know about what is inside our skull, and we may never. Perhaps another entirely different approach is needed, maybe?