They're often depicted as primitive and brutish – but Neanderthals were just as smart as humans, according to a study.

For years, it has been suggested that a difference in head shape meant the ancient species were less intelligent than their human contemporaries.

Despite having a larger skull it was believed they had inferior language skills, poorer mental abilities and smaller memory capacity, which contributed to their demise.

Now, experts have compared the brain anatomy of two distinct groups of modern–day humans and found larger differences than those reported between humans and Neanderthals.

This suggests any difference in intelligence between Neanderthals and humans would have been small.

'The question of why Neanderthals no longer exist has long been of interest,' the researchers, from Indiana University, wrote in the Proceedings of the National Academy of Sciences journal.

'Speculation on Neanderthal cognition based on archaeological and paleoneurological research has frequently concluded they were likely cognitively challenged.

'Putting estimated Neanderthal differences into the context of modern human variation does not support this view.'

For their study, the researchers compared the brains of two modern human populations using MRI data from 200 individuals of European descent in the US and 200 ethnic Han Chinese individuals.

They discovered that volume differences in particular parts of the brain were even larger between these two groups than between humans and Neanderthals.

Therefore, any average difference in cognition between Neanderthal and early modern human populations would have been negligible.

'It seems likely that any average cognitive differences that existed would have been very subtle, if detectable at all,' they wrote.

'While small differences in cognition can theoretically have large evolutionary effects over the very long term, it is critical to put the size of any such effects into proper comparative perspective.'

They also pointed out that recent research indicates any link between brain size and intelligence in modern humans is weak and not definitively proven.

The scientists said that before their demise Neanderthals were distributed across a large area, had extensive use of fire and cooking and were known to forage for a wide range of food.

The most likely reason for their replacement and extinction is due to genetic 'swamping' – with genes gradually being replaced by those of modern humans due to interbreeding – they explained.

The Neanderthals are believed to have lived between roughly 350,000 and 40,000 years ago, their populations spreading from Portugal in the west to the Altai mountains in central Asia in the east.

They vanished from the fossil record when modern humans arrived in Europe.

A separate study has also found 'no support' for the theory that modern humans were superior in a range of ways, including weaponry and hunting strategies.

That research, published in the journal Plos One, reads: 'Virtually all explanations for the disappearance of the Neanderthals from the Eurasian record point in one way or another to the arrival of Homo sapiens, anatomically modern humans (AMH), in Europe and western Asia.

'The disappearance of the archaic populations, including Neanderthals, is routinely explained in terms of the 'superiority' of modern humans.

'These include inventiveness and capacity for innovation, complex symbolic and linguistic abilities, more efficient hunting strategies, exploitation of a broader range of resources, projectile technology…and memory capacity.

'Inferiority in one or more of these domains has been at the core of many explanations for the demise of the Neanderthals.'

It concludes: 'We have found no data in support of the supposed technological, social and cognitive inferiority of Neandertals compared to their AMH contemporaries.'

Last month, scientists used research to recreate the lost language of ancient human species.

They said Neanderthals would have communicated in a language that our Homo sapien ancestors could understand and even engage with.

Archaeological evidence has shown that Homo sapiens and Neanderthals met and even interbred relatively frequently , which explains why many people today still have Neanderthal genes.

Due to the physiological differences between Neanderthals and modern humans, they still wouldn't sound quite like us.

Professor Steven Mithen, an expert on early prehistory from the University of Reading, told the Daily Mail: 'They would have sounded more nasal because of their large noses, could speak much louder and for longer periods without taking a breath because of their large chests and lung capacity.'

Professor Mithen's research also suggests that they would have used louder and more pronounced plosive 'p', 't', and 'b' sounds due to their larger lungs.

However, experts argue that Homo sapiens and Neanderthals would still have had some level of common understanding.

Professor Mithen says that Homo sapiens and Neanderthals would have been able to talk 'just as we can communicate with people who speak other languages today by using gestures and facial expressions'.