In the search to discover our origins, scientists have suggested many ideas that range from far-fetched to fascinating. From unlikely mutations to new types of humans, our gravitation towards such research shows how fascinated we are with our past. The latest crazy-sounding theory is that human limbs could have evolved from gills.
Scientists are now fairly certain human hands evolved from fins, but way back in 1878 when German scientist Karl Gegenbaur proposed fins evolved from gills, which would then mean limbs evolved from gills, his theory was thrown out because it couldn’t be confirmed in the fossil record. Now, over 100 years later, a research team led by University of Cambridge scientist Andrew Gillis is taking a second look.
Gillis approached the theory from a new angle: he manipulated the Sonic hedgehog gene found in both humans and cartilaginous fish like sharks, skates, and rays. In humans, the gene plays a role in how our fingers develop. Gillis’ research looked specifically at how the gene would function in skates, and found it’s intriguingly similar to humans.
The gill anatomy of cartilaginous fish bears a resemblance to human fingers: features called branchial rays, which help support the skin covering the gills, look very much like fingers. Gillis found that adjusting the Sonic hedgehog gene in the skate rays determined how and where the branchial rays would form, just as it determines how and where fingers grow. he said, “Gegenbaur speculated that gill arches and fins/limbs were evolutionary related because they appear to be built according to a common ground plan. We’ve identified a molecular feature that could be a key part of the ground plan.”
The research could provide new insight into our largely unknown past. So was Gegenbaur ahead of his time? Gillis said it’s not that simple. Perhaps fins and gills simply share the Sonic hedgehog gene, and aren’t connected. Gillis intends to dig into the topic further, and see if we are more closely connected to fish than we once thought.