August 24, 2010
How did humans develop such large brains? The conventional answer, from Darwin’s playbook, is that brainier individuals are more attractive and have thus been chosen as mates more often throughout history. According to archaeologist and anthropologist Timothy Taylor, however, the sexual selection mechanism doesn’t satisfy.
Walking upright requires a smaller pelvis, preventing babies’ heads from developing beyond a certain size in the womb. Taylor believes tool use - which predates modern humans by 300,000 years - allowed mothers to carry their babies in slings:
We used technology to turn ourselves into kangaroos. Our children are born more and more underdeveloped because they can continue to develop outside the womb - they become an extra-uterine fetus in the sling. This means their heads can continue to grow after birth, solving the smart biped paradox. In that sense technology comes before the ascent to Homo. Our brain expansion only really took off half a million years after the first stone tools. And they continued to develop within an increasingly technological environment.
Taylor also thinks technology helps to explain why our brains have been getting smaller in recent history:
Evidence shows that over the last 30,000 years there has been an overall decrease in brain size and the trend seems to be continuing. That’s because we can outsource our intelligence. I don’t need to remember as much as a Neanderthal because I have a computer. I don’t need such a dangerous and expensive-to-maintain biology any more.
One wonders how intelligence would have been outsourced before recorded history, since writing only developed around 6,000 years ago. But the idea that human biology has been shaped by technology is well documented. Read more from Taylor in this NewScientist interview, or check out his book, The Artificial Ape: How Technology Changed the Course of Human Evolution