No one doubts it Albert Einstein he had a great mind. But the Nobel laureate, famous for his theories of special and general relativity, was not blessed with a big brain. “It was smaller than average,” he says Jeremy DeSilva at Dartmouth College in New Hampshire.
That sounds amazing. Big brains are a defining feature of the human anatomy, and we’re proud of them. Other species may be fast or strong, but we thrive by using the ingenuity that comes with a big brain. Or so we tell ourselves. Einstein’s brain suggests that the story is not so simple, and recent fossil discoveries confirm this. In the last two decades, we have learned that small-brained hominin species survived on Earth long after the appearance of large-brained ones. Moreover, there is growing evidence that the behavior was sophisticated. Some, for example, made complex stone tools that could probably only be shaped by people with language.
These findings turn the question of the evolution of the human brain on its head. “Why would selection favor big brains when small-brained humans can survive in the landscape?” says DeSilva. Neural tissue consumes a lot of energy, so it must have benefited the few species that evolved large brains. But what?
An answer to this puzzle is beginning to emerge. It appears that brain expansion began as an evolutionary accident and then changes caused this growth to spiral. Surprisingly, the changes that drove this expansion may also explain the 10 percent reduction in human brain size. What’s more, this suggests that our brains could shrink even further, and even cause the death of humanity.
It is undeniable…
