The times they are a ‘changin’

IN YOUR FACE

Our brains have been shrinking over the last 30,000 years. The average volume of the human brain has decreased from 1,500 cubic centimetres to 1,350 cubic centimetres, which is equivalent to a chunk the size of a tennis ball.

There are several different conclusions: We could in fact be getting dumber. Historically, brain size decreased as societies became larger and more complex, suggesting that the safety net of modern society negated the correlation between intelligence and survival. But another, more encouraging theory says our brains are shrinking not because we’re getting dumber, but because smaller brains are more efficient (like phones and computers).

This theory suggests that, as they shrink, our brains are being rewired to work faster but take up less room. There’s also a theory that smaller brains are an evolutionary advantage because they make us less aggressive beings, allowing us to work together to solve problems, rather than tear each other to shreds.

SIGNS OUR BODIES ARE STILL EVOLVING

MILK

Our ancestors had much bigger jaws than we do, which helped them chew a tough diet of roots, nuts and leaves. And what meat they ate they tore apart with their teeth, all of which led to worn down teeth that needed replacing. Enter the wisdom teeth: A third set of molars is believed to be the evolutionary answer to accommodate our ancestors’ eating habits.

Today, we have utensils to cut our food. Our meals are softer and easier to chew, and our jaws are much smaller as a result, which is why wisdom teeth are often impacted when they come in — there just isn’t room for them. Like the appendix, wisdom teeth have become vestigial organs. One estimate says 35% of the population is born without wisdom teeth, and some say they will disappear altogether.

DISEASE RESISTANCE

Originally, we all had brown eyes. However, roughly 10,000 years ago, someone who lived near the Black Sea developed a genetic mutation that turned brown eyes blue. While the reason blue eyes have persisted remains a bit of a mystery. One theory is that they act as a sort of paternity test. There is strong evolutionary pressure for a man not to invest his paternal resources in another man’s child. Because it’s virtually impossible for two blue-eyed mates to create a brown-eyed baby, our blue-eyed male ancestors may have sought out blue-eyed mates as a way of ensuring fidelity. This would partially explain why, in a recent study, blue-eyed men rated blue-eyed women as more attractive compared to brown-eyed women, whereas females and brown-eyed men expressed no preference.