We share about 98.8 per cent of our DNA with chimpanzees, our closest living relatives. Yet, despite this near-identical genetic blueprint, chimps have not built civilisations, waged wars or mastered the art of the TikTok dance routine.
But what exactly sets us apart? Now, neuroscientists may finally have an answer.
A new study published in the journal JNeurosci has taken a fresh look at data from the brains of humans, chimpanzees and macaques – another well-studied species of primate.
“We were interested in finding out what makes different brains tick,” Prof Rogier Mars, co-author of the study, told BBC Science Focus. “And the human brain, for obvious reasons, is one that we were particularly interested in.”
According to Mars, most studies comparing human brains to those of other animals tend to focus on factors like overall size, the size of specific regions or the number of neurons. “But our philosophy is that if you want to truly understand what’s happening, you need to examine how the brain is organised,” he said.
With that approach in mind, Mars and his team set out to investigate. Using publicly available MRI data – similar to the scans used in hospitals – they created “connectivity blueprints” of the brains in the three different species. These blueprints essentially map how much different regions of the brain talk to one another.
One area the team expected to find differences was in the prefrontal cortex – a region linked to complex thought, planning and decision-making.
Often called the brain’s ‘personality centre’, this area plays a crucial role in regulating emotions and guiding behaviour. At first glance, it seems like the obvious place to search for the essence of what makes us human. Indeed, the study revealed that this area showed more connectivity than in the other species.
But was that the whole story?
“The prefrontal cortex is where researchers tend to look when searching for something uniquely human,” Mars said. “But we found differences in lots of places, particularly in the temporal cortex, which is just above your ear. These seemed to be much more wired up to the rest of the brain in humans than in any other species.”
The temporal cortex plays a key role in processing sensory information — particularly sight, sound and language. Given our highly social and cooperative nature, it’s perhaps no surprise that these areas are more intricately connected in the human brain.
“We’re a very social and collaborative species,” Mars explained. “So those traits are likely the driving force behind the changes we observe.”
All of this suggests that there isn’t a single defining switch that makes humans, well, human. While some believe that a pivotal evolutionary event propelled us to dominance, the reality is likely more complex.
Like our not-so-distant relatives in the trees, we are the result of gradual, far-reaching evolutionary changes that have shaped us over time.
Or, as Mars put it: “There’s not one big thing that makes us different; it’s a bunch of little things.”
About our expert
Rogier Mars is a professor of neurosciences at the University of Oxford. His work focuses on the the difference between primate brains, especially humans. Mars' research has been published in journals such as Nature Communications, Frontiers in Human Neuroscience and Science.
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