London: Neanderthals became extinct because they had larger eyes than modern humans, a new study of skulls of the now extinct species has suggested.
As Neanderthals had larger eye, researchers believe more of their brain was devoted to seeing in the long, dark nights in Europe, at the expense of high-level processing, according to the BBC.
Neanderthals are a closely related species of human that lived in Europe from around 250,000 years ago. They coexisted and interacted briefly with our species until they went extinct about 28,000 years ago, in part due to an ice age, explained researchers of the study, which is published in Proceedings of the Royal Society B Journal.
The research team wanted to explore the idea that the ancestor of Neanderthals left Africa and had to adapt to the longer, darker nights and murkier days of Europe. The result was that Neanderthals evolved larger eyes and a much larger visual processing area at the back of their brains.
The humans that stayed in Africa, on the other hand, continued to enjoy bright and beautiful days and so had no need for such an adaption. Instead, these people, our ancestors, evolved their frontal lobes, associated with higher level thinking, before they spread across the globe.
Eiluned Pearce of Oxford University decided to check this theory.
She compared the skulls of 32 Homo sapiens and 13 Neanderthal skulls and found that Neanderthals had significantly larger eye sockets - on average 6mm longer from top to bottom.
Although this seems like a small amount, she said that it was enough for Neanderthals to use significantly more of their brain to process visual information.
Since Neanderthals evolved at higher latitudes, more of the Neanderthal brain would have been dedicated to vision and body control, leaving less brain to deal with other functions like social networking, she explained to BBC News.
Prof Chris Stringer, an expert in human origins at the Natural History Museum in London but also involved in the research, also agreed.
"We infer that Neanderthals had a smaller cognitive part of the brain and this would have limited them, including their ability to form larger groups. If you live in a larger group, you need a larger brain in order to process all those extra relationships," he said.
The researchers also assumed that the Neanderthals more visually focused brain structure might also have affected their ability to innovate and to adapt to the ice age that was thought to have contributed to their demise.
The results contradict emerging research that Neanderthals were not the stupid brutish creatures portrayed in Hollywood films, but may well have been as intelligent as our species.
Oxford University`s Prof Robin Dunbar, who supervised the study, said that the team wanted to avoid restoring the stereotypical image of Neanderthals.
"They were very, very smart, but not quite in the same league as Homo sapiens," he told BBC News.
He suggested that the difference might have been enough to tip the balance when things were beginning to get tough at the end of the last ice age.