Prehistoric man looked to eyebrows to make contact

EYEBROWS are crucial to human evolution, scientists have discovered, because they were instrumental in how our predecessors learnt to communicate.

The development of highly mobile brows to express emotions helped early humans convey nuanced messages of recognition or sympathy, research by York University found.

Scientists believe this was crucial to survival because it enabled them to work together, rather than alone in the wild. It is also probably why modern humans have developed a smooth forehead with more visible brows, compared to the pronounced brow of early hominins, they said.

The team used 3D engineering software to study the brow ridge of a fossilised skull known as Kabwe 1, from between 200,000 and 600,000 and years ago.

They then discounted two theories commonly put forward to explain its protruding brow ridges – one being that they were needed to fill the space where the flat brain cases and eye sockets of archaic hominins met, and the second being that it acted to stabilise their skulls from the force of chewing.

It led them to the theory that the evolutionary changes were linked to social factors.

Prof Paul O’higgins said: “We suggest a plausible contributing explanation can be found in social communication.”

The researchers explained communicative foreheads started off as a sideeffect of our faces getting gradually smaller over the past 100,000 years.

They said the process sped up in the past 20,000 years as we switched from hunter gatherers to agriculturalists – a lifestyle with less variety in both diet and physical effort.

Dr Penny Spikins, of York’s department of archaeology, said: “Modern humans are the last surviving hominin. 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 large social networks – we know, for example, that prehistoric modern humans avoided inbreeding and went to stay with friends in distant locations during hard times.”

Dr Spikins says in the study that eyebrow movements allow us to express complex emotions, as well as perceive the emotions of others. A rapid “eyebrow flash”, for instance, is a “crosscultural sign of recognition and openness to social interaction”, while “pulling our eyebrows up at the middle is an expression of sympathy”.