Breakthrough! Fingers May Have Evolved From Fish Fins, Study Says
Evolution has come a long way throughout history, and a recent study reveals that human fingers may have originated from fish fins.
According to a study published in the journal Nature, scientists from the University of Chicago found, via gene-editing and fate mapping, that bones at the end of fish fins are extremely flexible like those in human fingers and toes. They also discovered that cells found in fins are the ones responsible for forming fingers and toes of land animals.
"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. Our results change that whole idea. We now have a lot of things to rethink," said Neil Shubin, senior author of the study from the Robert R. Bensley Distinguished Service Professor of Organismal Biology and Anatomy at the University of Chicago, via Phys.org.
Shubin, Tetsuya Nakamura and Andrew Gehrke studied the growth of the zebrafish by deleting its Hox genes, which are responsible for planning the embryo's body from the head to its tail as well as its fingers and shoulders. The scientists then bred this "mutant" species and then cross-bred them, observing them as they grow.
"What matters is not what happens when you knock out a single gene but when you do it in combination. That's where the magic happens," Nakamura said.
The results show that when Hox genes were deleted in zebrafish, the length of the animals' fins decreased. Also, by using a high-energy CT scanner, scientists found out that the adult zebrafish with deleted Hox genes lack fin rays but there's a dramatic increase in small bones made of cartilage.
"It really took the combination of labeling and knockouts to convince us that this cellular relationship between fins and limbs was real," Gehrke said.