Cosmetically minded? Research suggests Neanderthals had developed a taste for self-adornment and makeup. Photograph: Science Photo Library

For decades, our low-browed Neanderthal cousins have been portrayed as dim savages whose idea of seduction was a whispered "ug" and a blow to the cranium.

But analysis of pierced, hand-coloured shells and lumps of pigment from two caves in south-east Spain suggests the cavepeople who stomped around Europe 50,000 years ago were far more intelligent – and cosmetically minded – than previously thought.

In 1985, archaeologists excavating the Cueva de los Aviones in Murcia found cockle shells perforated as if to be hung on a necklace and an oyster shell containing mineral pigments, hinting that the cave's Neanderthal residents had developed a taste for self-adornment and makeup.

Twenty-three years later, an expedition led by João Zilhão, professor of palaeolithic archaeology at the University of Bristol, turned up a pierced, orange-­coloured scallop shell bearing traces of red and yellow pigment at another Murcian cave, Cueva Antón.

Despite its significance, however, the latter find was nearly overlooked.

"The shell was found by an undergraduate student at Bristol on the first or second day of the dig," said Zilhão. "When he showed it to me I told him it was probably a fossil from the cave wall. Note it and bag it, I said, we'll look at it later. We forgot about it till later and then, when we were cleaning it, I realised that it was a shell, not a fossil."

It was then, said the professor, that it occurred to him the shell might corroborate the finds at Cueva de los Aviones, and prove that Neanderthals were more sophisticated than they had been given credit for.

Analysis of the reddish residues from the oyster shell from Cueva de los Aviones had found a pigment made up of minerals including lepidocrocite, haematite, pyrite, and charcoal.

The orange scallop shell found in Cueva Antón, meanwhile, had been coloured with red haematite and yellow goethite and was probably part of a necklace.

The small quantity of pigment recovered in the oyster shell also led the archaeologists to speculate that it had been made for use on the body. According to Zilhão, the effect of the darkly sparkling preparation would not have been too different from today's coruscating skin powders.

"The idea that came to our minds was that it was some kind of glitter or makeup like the shimmery stuff that people were wearing a few years ago," he said.

"Its preparation makes no sense unless it was used as a body cosmetic. We can't prove it but it makes sense."

As well as yielding evidence of mining, transportation and the ability to work to a complex recipe, said Zilhão, the existence of the cosmetics also provides an insight into Neanderthal psychology. "They are clearly used as something to convey ideas and to decorate the face and body. It shows a symbolic dimension in behaviour and thinking that cannot be denied – especially when found in connection with the perforated and decorated shells."

What's more, said the professor, the oyster shell, which was also held in high-esteem by cultures in pre-Columbian America, was also found near a quantity of yellow natrojarosite, a mineral pigment whose cosmetic properties made it a favourite of the ancient Egyptians.

Radiocarbon dating of the samples was carried out by the University of Oxford's radiocarbon accelerator unit. Their tests established that the shells and charcoal found in the two caves could be traced back to around 50,000 years ago – around 10 millennia before the first appearance in Europe of early modern man. All of which, reckons Zilhão, shows that Neanderthals were doing many of the same things as their early modern human counterparts in Africa.

"Whether that means that the Neanderthals were as smart as early modern humans or that early modern humans were as stupid as Neanderthals depends on how you look at the past," he said. "My view is that there's absolutely no scientific justification to consider Neanderthals as the brutish halfwits they have been portrayed as in popular culture – which has also, to a certain extent, influenced scientific thinking."

It was high time, he added, to banish our caveman prejudices. "Even if they were a bit different in behaviour and cognition, they were as human as their contemporaries, who we call our ancestors."

The findings are published in the journal Proceedings of the National Academy of Sciences.