New research demonstrates that the evolutionary antecedent of human hands and feet is actually the fish fin.
Just like any layperson with a working set of eyes, scientists long believed that our hands and fingers (not to mention the hands and feet of all land-dwelling creatures in our planet’s history) did not directly evolve from the thin, bony rays found in fish fins. That belief helped support the overarching theory that the hands and feet that allowed the very first creatures to rise out of the water and onto land hundreds of millions years ago composed a wholly new evolutionary leap with no direct predecessor.
New research conducted at the University of Chicago and published in Nature, however, recasts this crucial moment in the history of life on planet Earth.
The momentous revelation that there’s a direct evolutionary line between Earth’s last exclusively water-dwelling creatures and first land-dwelling creatures comes courtesy of just two genes: Hoxa-13 and Hoxd-13, the ones responsible for limb growth.
The Chicago team (led by Neil Shubin, responsible for the discovery of Tiktaalik, the creature that is likely the evolutionary link between water-dwellers and land-dwellers) was able to show that if they blocked these two genes in fish, the fin rays wouldn’t fully form. Similarly, the researchers found that if they marked the cells marshaled by Hoxa-13 and Hoxd-13 during limb growth with a kind of glowing dye, then the fin rays, once formed, would indeed glow.
Thus, the researchers were able to show that the same genes, acting in the same way, are responsible for the development of everything from fish fins to human hands.
Once again, evolutionary biology has proven that we humans aren’t as special as we’d often like to think.