Lungs, not limbs, propelled the aquatic ancestor of land animals out of the ocean, according to a new analysis of the genome of the coelacanth, an ancient species of fish with limblike fins. Scientists have debated whether fish with lungs, such as lungfish, or fish like coelacanths were the so-called “fish that first crawled onto land.”
Coelacanths, Latimeria chalumnae and Latimeria menadoensis, are often called living fossils because of their resemblance to specimens dating back 300 million years. But the fish’s DNA isn’t a relic stuck in the past. It is still evolving, just more slowly than the DNA of most other animals, an international group of researchers reports April 18 in Nature.
By comparing the genome of the African coelacanth, L. chalumnae, to that of other vertebrates, the researchers pinpointed genetic changes that enabled animals to live on land. The transition involved losing many genes — including eight involved in ear development and 13 in fin development — and changing how others are used.