Curly hair kept early humans cool and made our brains bigger, study finds

Lots of different wigs were used in the experiment, and it was found that tighter curls were better at protecting humans from heat

Humans may have evolved to have curly hair in order to avoid the worst of the heat and to keep water in the body, a new study has found.

Scientists from a number of universities, including Loughborough in the UK and Penn State in America, were looking at how different hair textures can help to regulate body temperature.

They found that curly hair kept humans cool and allowed them to conserve water in the body. The scientists believe both these things contributed to humans being able to grow their brains to modern-day sizes.

The tightest curls can usually be found in afro hair

This happened because the earliest humans lived in one of the hottest parts of the world, as Penn State scientist Nina Jablonski explained: "Humans evolved in equatorial Africa, where the sun is over head for much of the day, year in and year out.

"Here the scalp and top of the head receive far more constant levels of intense solar radiation as heat. We wanted to understand how that affected the evolution of our hair. We found that tightly curled hair allowed humans to stay cool and actually conserve water."

How did scientists find this out?

The research team at Loughborough University used something called a thermal manikin to conduct the experiment.

It's a human-shaped model that uses electricity to simulate body heat on the skin.

Here you can see the manikin in the room at Loughborough University where it was studied

The manikin was programmed to remain constantly at 35 degrees Celsius, similar to the average surface temperature of human skin.

Scientists measured how much electricity was needed to maintain that temperature when wigs with different hair textures were used.

The researchers say this way of studying human hair is exciting as it means experiments can take place without using any actual people and potentially exposing them to risk

They also used solar lamps and wind tunnels to replicate the heat and humidity found in countries near the equator.

While all hair types retained heat and protected the scalp from harmful radiation from the sun, they found tightly curled hair provided the best insulation and protection.

How did humans get so brainy?

The scientists involved in the study believe this is how our brains evolved to be as big as they are today.

The brain is very sensitive to heat, and it also creates heat - the bigger it is, the more it can create.

However, if it gets too hot, it can make you very sick.

The scientist believe having hair on our heads meant our brains could get bigger over time

Humans have sweat glands that keep us cool, but they aren't enough to prevent dangerous overheating in the brain.

One of the researchers at Penn State called Tina Lasisi said this is why humans evolved to have lots of hair on the tops of our heads, even when we lost much of it elsewhere on our bodies.

"We think scalp hair provided a passive mechanism to reduce the amount of heat gained from solar radiation that our sweat glands couldn't," she said.