In 1878, famed German anatomist Karl Gegenbaur presented a rather peculiar theory stating that human limbs have evolved from gills of cartilaginous fishes, including sharks and skate.
But the scientific community at that time was quick to debunk Gegenbaur’s theory for lack of supporting evidence, particularly fossil evidences. But by using high precision genetic analysis of skates’ embryos, particularly the Sonic hedgehog gene, it was learned that the developing embryos share genetic mechanism with human limbs.
According to the study conducted by zoologists from Cambridge University, the latest data showed a link between gills of cartilaginous fish and the origin of the human limbs and other jawed vertebrates. The study, which was published in The Company of Biologists, is the first study that provides striking evidence of Gegenbaur’s theory 138 years ago.
University of Cambridge Professor Dr Andrew Gilli, as reported by the Phys.org, said Gegenbaur was probably right after all on his theory on the origin of the human limb. Gilli added that the structure of the skate embryo’s branchial rays and how it connects to the gill arches resembles how the limb skeleton connects to the shoulder.
“The fact that the Sonic hedgehog gene performs the same two functions in the development of gill arches and branchial rays in skate embryos as it does in the development of limbs in mammal embryos may help explain how Gegenbaur arrived at his controversial theory on the origin of fins and limbs.”
The research team has also theorized that it could be possible that Gegenbaur took note of the mechanism of the Sonic hedgehog gene in the development of gill arches and branchial rays in skates, since it’s much closer to the development of limbs in human embryos and other mammals.