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The common ancestor of humans may have had tentacles, a scientist has claimed.

Organisms that lived in the sea 635 to 541 million years ago, from which humans and other animals evolved, likely had flexible appendages and a complex nervous system.

It seemingly puts to bed another theory that suggests our ancestors were much more simple, worm-like creatures.

A Russian scientist says the distant ancestor of humans had tentacles. One such creature can be seen at the centre of this illustration. They lived more than 540 million years ago and used them for food. It's likely they also had a complex nervous system like we do today

The latest research was conducted by Dr Elena Temereva from the Department of Invertebrate Zoology at the Faculty of Biology of the Lomonosov Moscow State University.

Today, humans and many other organisms are bilaterally symmetric - we have a clearly discernible top and bottom, and a left and a right.

However, our distant ancestors hundreds of millions ago were not, with many of them thought to be worm-like creatures that swam in the seas or walked on the seafloor.

How we evolved into bilateral creatures, and what we evolved from, has been a cause of some debate.

One theory suggests that our common bilaterian ancestor was a worm without appendages and just a simple nervous system.

Dr Temereva's research, though, favours a different theory. She says that our ancestors had appendages - or tentacles - that were used for movement and food collection.

And, she says, they also had a complex nervous system.

To come to her conclusion she studied Lingula anatina, an ancient brachiopod found all over the world.  

Lingula is one of the oldest brachiopods having survived to the present day, originating in the Early Ordovician era 500 million years ago.

For that reason, and as it has hardly changed over geological time, it is often referred to as a 'living fossil' of organisms in the distant past.

Today, humans and many other organisms are bilaterally symmetric; we have a clearly discernible top and bottom, and a left and a right - such as depicted in da Vinci's The Vitruvian Man, shown left. Dr Elena Temereva came to her conclusion by studying the 'living fossil' Lingula anatina, shown right

'By virtue of the fact that there are tentacles among the two main taxons of bilaterally symmetrical animals, it is logical to assume that the common ancestor also had them,' said Dr Temereva.

'It means that the common ancestor of chordate animals [such as mammals, fish and birds] including people also had tentacles.'

She said that, therefore, it could be assumed that our ancestors had tentacular appendages.

It is hoped that this research will help to more accurately classify various species.#

The results are published in the journal Plos One.