New study discovers a human body part evolved from fish

As one theory suggests, all life on Earth began in a hot spring. Microorganisms formed, and over a process of millions of years, these organisms turned into bigger organisms, which eventually made it onto land. So the idea that humans came from the sea is nothing new. But, as one new research has revealed, evolution did recycle old body parts (stock image) (Picture: Getty)

This new study revealed that our outer ears could have evolved from the gills of prehistoric fish. What does this mean, exactly? Well, researchers already know that our middle ears – the part that sits behind the eardrum and is made up of three small bones, came from the jawbones of ancient fish. But gene-editing experiments suggest that cartilage in fish gills migrated into the ear canal millions of years ago during the course of our evolution. This new research sheds light on the origins of our outer ears (stock image) (Picture: Getty)

Study co-author Gage Crump, a professor of stem cell biology and regenerative medicine at the University of Southern California, said: ‘When we started the project, the evolutionary origin of the outer ear was a complete black box. We had been studying the development and regeneration of the jawbones of fishes, and an inspiration for us was Stephen Jay Gould’s famous essay “An earful of jaw”, which laid out how fish jawbones transformed into the middle ear bones of mammals. This made us wonder whether the cartilaginous outer ear may also have arisen from some ancestral fish structure’ (stock image) (Picture: Getty)

So what did they do? The researchers say that the first clue was that gills and outer ears are both composed of a relatively rare tissue type: elastic cartilage. It wasn’t really known if fish had elastic cartilage or not but ‘it turns out that they do’ Dr Crump said. The researchers tested the evolutionary link between elastic cartilage in fish gills and mammalian outer ears. Elastic cartilage doesn't preserve well in fossils, so the researchers used molecular clues instead (stock image) (Picture: Getty)

The researchers looked for gene control elements called ‘enhancers’ which are short DNA sequences that can activate associated genes when bound by specific proteins. As genetic enhancers are highly tissue-specific, researchers can easily detect where the enhancers are active. And to test if the material in fish gills was similar to human outer ears, Dr Crump and his colleagues inserted human outer ear enhancers into zebrafish genomes (stock image) (Picture: Getty)

The experiment ended up triggering activity in the gills of zebrafish, which suggested an ancestral link between the genes in human outer ears and fish gills. But to check their work, the researchers did it in reverse and inserted enhancers associated with zebrafish gills into mouse genomes. They detected activity in the mice's outer ears (stock image) (Picture: Getty)

Dr Crump said: ‘This work provides a new chapter to the evolution of the mammalian ear. While the middle ear arose from fish jawbones, the outer ear arose from cartilaginous gills. By comparing how the same gene control elements can drive development of gills and outer ears, the scientists introduce a new method of revealing how structures can dramatically change during evolution to perform new and unexpected functions’ (stock image) (Picture: Getty)