Charles Darwin showed how our ancestors evolved from water to land mammals and now scientists have cracked the mystery of how fins evolved into the hands we use today.

A team of researchers from the University of Chicago have used new gene-editing techniques to examine the connection between the formation of fish fins and finger digits of humans. You may be mistaken in thinking fins just gradually turned into fingers over millions of years but the two are actually completely different bones formed in different ways meaning it isn’t possible for the fin to just evolve.

“For years, scientists have thought that fin rays were completely unrelated to fingers and toes, utterly dissimilar because one kind of bone is initially formed out of cartilage and the other is formed in simple connective tissue,” stated Neil Shubin, a biologist at the University of Chicago involved in the study. “Our results change that whole idea. We now have a lot of things to rethink.”

However, looking into the genes of zebrafish, the team discovered an overlap between the genes involved in fin formation and the genes found in the formation of fingers in humans.

The two genes were HoxD and HoxA – these genes steer the blueprint of an embryo in terms of fin development in fish and wrist and digit development in mammals. Through experimentation, the research team found that without these two genes, mice were unable to develop fully functioning wrists and toes and when taken out of the zebrafish, the fish didn’t develop their long fin rays showing a strong previously unknown connection.

“It was totally against my expectations,” says Shubin. “If digit development and fin development were truly distinct processes, “the markers of the wrists and digits should end up in the cartilaginous bones, which sit at the base of the fin, not in the fin rays.” 

Shubin and his team are planning to do further research but the discovery has definitely helped us understand the evolutionary process that Darwin presented to us back in the 1800s.

Details of the research was published in the journal Nature.