Humans have very flexible brains. We can change our behaviour quickly to adapt to new circumstances. But when we talk about these flexible brains, we aren't simply using a metaphor.
New research has identified our brains are actually physically flexible. The structure of our brains can actually change in response to environmental, social, and cultural factors.
The scientists behind this study weren't able to identify the specific factors that cause these changes. However, it does seem likely that this literal flexibility is what helps our behaviour be so malleable.
Flexibility makes humans special
Flexible behaviour is one of the big reasons our species is so successful. It makes it possible for us to learn from one another, adapt to different environments, come up with new ways of doing things, and so much more.
In fact, the ability to come up with new behaviours and change the way we do things is often listed as one of the key things that makes humans special. Many argue that it's why we were able to outcompete the Neanderthals and drive them to extinction. Those silly Neanderthals didn't have that flexibility and so wound up making the same set of tools for hundreds of thousands of years. Humans, on the other hand, were much better innovators. So we could come up with fancier tools!
As such, understanding why humans have such flexible behaviour is pretty important to understanding our species. Which is where this new research comes in.
Stuck in the mud chimps
The researchers studied how malleable brains are by comparing the brains of closely related individuals. They mapped "landmarks" on the cortex and compared how different they were in these individuals.
If genes were the big thing that influenced the structure of our brains then these individuals should have very similar brains. After all, being closely related they would have very similar genes. On the other hand, if external factors influenced brain structure then there could be a fair bit of difference even between closely related individuals. What they learnt, where they worked, the "culture" they lived in could all potentially influence brain structure. This sort of family-based comparisons (called pedigree studies) are similar to the twin studies you may have heard of (where twins are compared to study this sort of thing). Classic examples involve comparing twins to see if there is a genetic basis for various diseases, like schizophrenia.
When they carried out this study on chimps they found that the brain structure of closely related individuals was very similar. This indicates that genes are what's mostly responsible for the shape of their brain. Of course, it's worth noting that genes alone weren't the only thing responsible; there still was some variation between these individuals.
Flexible humans
When they repeated this experiment in humans they found that the brain structure of closely related individuals often varied quite a bit. Which you probably already knew based on the title of this post. Putting that flexible brain to good use I see.
But perhaps more interesting is the flexibility within this flexibility. Not all regions of the human brain are equally malleable. The more "basic" parts of the brain they examined tended to have a pretty large genetic influence and didn't change much between individuals.
On the other hand, the more "modern" parts of the brain were more variable. These are modern in the sense that they've changed a lot over the course of human evolution and so are thought to be linked to all the shiny new cognitive abilities we developed. They're not unique to us, they just changed a lot in us. For example, they found that the length of the frontal lobe varied quite a bit between individuals. The frontal lobe is one of those associated with movement and houses a lot of stuff linked with language, including the famous Broca's area.
So, it would seem a key part of human evolution was not just changing stuff like the frontal lobe; but also allowing the frontal lobe to become more flexible and change over the course of an individuals life time. This increased plasticity could be one of the reasons humans seem so smart; although much more research is needed on this topic.
tl;dr
Humans behaviour is very flexible. New research reveals this may be enabled by physically flexible brains. Their structure actually changes in response to environmental factors. Chimps, meanwhile, seem to have very "stuck" brains that are a lot less variable.
References
Bocquet-Appel, J. P., & Tuffreau, A. (2009). Technological responses of Neanderthals to macroclimatic variations (240,000-40,000 BP). Human Biology, 287-307.
Gómez-Robles, A., Hopkins, W. D., Schapiro, S. J., & Sherwood, C. C. (2015). Relaxed genetic control of cortical organization in human brains compared with chimpanzees. Proceedings of the National Academy of Sciences, 201512646.
Villa P, Roebroeks W (2014) Neandertal Demise: An Archaeological Analysis of the Modern Human Superiority Complex. PLoS ONE 9(4): e96424.
