The ability to convey emotion through the eyebrows, whether raised or twitched into a frown, may have been key to human survival, a new study has found.

The study published in the journal Nature Ecology and Evolution conveys that the move of a brow can start friendships, enable social communication, build cooperation and allow for a greater understanding between modern humans.

The large brow ridges on a fossilised skull of the Kabwe 1, an early human species which lived up to 600,000 years ago, was studied by researchers from the University of York, in the United Kingdom.

They found that distinctive, thick-boned, immovable brows were a permanent sign of dominance and aggression in archaic humans.

It helped early humans, who had yet to develop language skills, communicate with others in the wild.

Model of a modern human skull next to Kabwe 1. Photo: Professor Paul O’Higgins, University of York.

The researchers behind the study note how humans are able to use their moveable brows to express an array of emotions. This is thanks to human evolution and the development of flatter, smoother foreheads, they theorise.

Two commonly proposed theories to explain why early humans had large brow ridges – to fill the space where the flat brain cases and eye sockets met and/or stabilise their skulls from the force of chewing – were discounted by the researchers.

Co-author of the paper, Dr Penny Spikins, from the department of archaeology at the University of York, said: “Modern humans are the last surviving hominid.”

“While our sister species, the Neanderthals, were dying out, we were rapidly colonising the globe and surviving in extreme environments. This had a lot to do with our ability to create a large social network.

“Eyebrows are the missing part of the puzzle of how modern humans managed to get on so much better with each other than other now-extinct hominids.”

Allan Pease, author of the The Definitive Book of Body Language, rates eyebrows as “critical” for the survival of the human race.

The body language expert said when you meet someone for the first time, the first thing you are likely to do is raise your eyebrows.

“You’re acknowledging that the other person is here in your presence, which makes the other person feel somewhat attracted to you. They find you interesting because [the gesture] acknowledges that they’re here,” Mr Pease said.

“A lot of people do that anyway without being aware of it, but a lot of people don’t, particularly men.”

He said this is crucial because, when you meet a person for the first time, you form up to 90 per cent of your impression about them in under four minutes. And a large part of the success of the encounter depends on the ability to interpret the emotions in another person.

“Eyebrows are the most noticeable part of the face that can show emotion.”

“If they’re shaved off, you’re less likely to be able to read the emotion in someone’s face, therefore you’re less likely to know how they’re feeling about anything.”

Also, the shape of the eyebrow can affect how you are perceived by others.

If your eyebrows are angled down towards your nose, people are less likely to talk to you.

“When people meet you, they somehow feel there’s something you’re not happy about you, so they stand further back. They talk to you less and they’re less likely to cooperate because you look like you could be angry,” Mr Pease said.

Curved eyebrows give off a friendlier vibe. As for those massively bushy eyebrows, Mr Pease said they should be groomed if you don’t want to look much older than your actual age.

As for President Donald Trump: “He needs a grooming expert to get in there and fix his hair and fix his eyebrows.

“His eyebrows are out of control. It shows age first of all, and to women it shows the guy doesn’t care much about his appearance.”