Tom Levitt, MSN Environment Editor

Your inner fish: how we owe our bodies to marine life

We share many anatomical features with fish (Image © Steven Senne/AP/PA Photos)

They may not look as similar to us as apes or monkeys, but fish and humans share several key bodily features. We explore the deep evolutionary connection.

All it took was one fossil. But as soon palaeontologists from the University of Chicago had found the well-preserved relic, a link between fish and land-based creatures was made.

The fossil had fins, scales and gills just like any other fish. But it also had eyes on top of its skull like a crocodile, ribs to facilitate breathing and shoulders unconnected to its skull giving it a neck. All features not usually present in fish.

A fossil showing evidence of a skull, shoulder and other parts that are common to land animals (image © Johnny Green/PA Archive/PA Photos)

So what does this tell us?

‘It tells us 3.5 billion years of the history of the human body,’ says Dr Neil Shubin, who led the team of fossil experts that made the discovery.

‘Our family tree extends to include all life on the planet. Our basic bone structure comes down to fish; for example, two eyes, two ears and a jaw. Much of what we use to communicate everyday we have inherited from fish,’ explains Dr Shubin, who has written a book on the link: Your Inner Fish.

He argues that while we may all have unique individual characteristics, many of our bodily features are shared with creatures that are found across the planet. For example, you might be surprised to learn that parts of our ear are the same as sharks.

‘Everyone at the zoo is looking at the primates; the gorillas, the chimpanzees and the orang-utans. They’re looking for that connection through the head and the eyes. But if they could look beyond that they would see a deeper connection,’ he adds.

A fossil showing evidence of fish scales and fins as well as wrists, fingers, ribs and a neck like a land animal (image © Johnny Green/PA Archive/PA Photos)

The discovery

As a palaeontologist, Dr Shubin had been concerned purely in finding a fossil that could bridge that gap between land and sea fish. But once his team had made that initial discovery, he realised he could be looking at much more than a link between sea and land. He concluded he had stumbled upon the origin of human life itself.

‘You cannot help but be dazzled by the deep connections we share with all animals, from worm-like creatures deep below the surface, to fish, to amphibians, to reptiles, to mammals and to primates.

‘Everything we have is from other species,’ says Dr Shubin.

‘The simplest way to teach students the nerves in the human head is to show them the state of affairs in sharks. The reason is that the bodies of fish and other creatures are often simpler versions of ours.’

Overlooking the Irish Sea, the Mourne Mountains in Northern Ireland are said to have been C.S Lewis’ inspiration for the magical land of Narnia

Our weakness

Shubin’s theory could offer us more than just a deeper understanding of where we come from. It may also help scientists learn more about the human body and even help us look for cures to diseases.

Unfortunately, not everything we might have inherited from our aquatic relatives has equipped us for modern life.

‘Our basic structure evolves from species that swim in seas,’ concludes Dr Shubin. ‘Hence some of the problems we have with wear and tear when we walk around on our ankles and knees. We didn’t evolve to ski, or to live life until we are 80-years-old.’

Further Reading

Video: fish fossil that led to the human link

Britain's marine wildlife

How to eat fish sustainably

Record-breaking animals

The wildlife quiz

Could we live in space?