A single genetic change could have enabled vertebrates to leave the water for the land, the Economist reports.
A Harvard University-led team of researchers conducted a genetic screen of zebrafish through which they uncovered gain-of-function mutations that led the fish to grow pectoral fins with extra bones. As they further report in the journal Cell, these extra bones resemble long bones and they integrated into the musculature and formed joints.
"Once we took a closer look at the skeleton ... we noticed that the pectoral fin had these extra bones that should never be there, and this really kind of knocked us off our feet," first author Brent Hawkins from Harvard University tells The Scientist.
The researchers traced the mutations spurring the development of these extra fin bones to the wasl and vav2 genes, both of which encode signaling proteins, but have not before been linked to body patterning. But gain-of-function mutations in both do increase the expression of the hoxa11b gene, and Hox11 genes are known to be involved in forearm development.
The Economist notes that the finding could give insight into how the ancestor of land vertebrates was able to come ashore.