No one doubts that Albert Einstein had a brilliant mind, but the Nobel Prize winner famous for his theories of special and general relativity wasn’t blessed with a big brain: “It was smaller than average,” says Jeremy DeSilva of Dartmouth College in New Hampshire.
This seems surprising. Big brains are a defining feature of human anatomy, something we are proud of. Other species may be faster or stronger, but we thrive using the ingenuity that comes from our big brains. At least, that’s what we tell ourselves. Einstein’s brain suggests that the story is not so simple, and recent fossil discoveries bear this out. In the past two decades, we’ve learned that small-brained hominin species persisted on Earth long after species with larger brains emerged. Moreover, there is growing evidence that they were behaviorally sophisticated. Some, for example, made complex stone tools that could only have been made by humans with language.
These findings turn a question about the evolution of the human brain upside down: “Why would large brains be selected for when humans with small brains can survive in nature?” says DeSilva. Because nervous tissue consumes a lot of energy, large brains must have undoubtedly provided an advantage to the few species that evolved them. But what was the benefit?
The answer to this mystery is beginning to emerge. It appears that brain expansion began as an evolutionary accident that then led to changes that accelerated brain growth. Amazingly, the changes that drove this expansion also explain the recent 10 percent shrinkage of the human brain. What’s more, this suggests that our brains could shrink even further, potentially causing our demise.
There’s no denying that…
