'Living Fossil' Genome Explains Why it Wasn't Affected by Evolution

Coelacanth, a deep-sea fish which became known as a "living fossil", has not changed in appearance since before the time of the dinosaurs roamed the earth and sky with the help of an extraordinary genome that is barely evolving, a study has found.

Researchers have sequenced the genome of the coelacanth, a deep-sea fish that closely resembles its ancestors, which lived at least 300 million years ago.

The prehistoric-looking blue creature was pulled out of the water in 1938 by a South African fisherman. It's a 1.5-metre-long coelacanth, a type of fish that had been thought to have become extinct 70 million years earlier. It can grow up to two meters (6.5 feet) in length and weigh as much as 91 kilos (200 pounds). Coelacanths have four large, fleshy fins, which some scientists believe could have been the predecessors of limbs.

The genetic blueprint appears to have changed astonishingly little over the aeons, pointing to one of the most successful species ever investigated, according to the study published in the journal Nature.

"We found that the genes overall are evolving significantly slower than in every other fish and land vertebrate that we looked at. This is the first time that we've had a big enough gene set to really see that," said Jessica Alföldi, a research scientist at the Broad Institute of MIT and Harvard in Massachusetts.

The coelacanth has changed so little over the last 400 million years that it might reveal how fish first grew limbs and walked on land.Charles Darwin first coined the term "living fossil" to describe species that have endured unchanged due to limited competition with other animals. However, Dr Alfoldi said that the description is not always helpful because it suggests a relic from the past that has been brought back to life.

"It's not a living fossil; it's a living organism. It doesn't live in a time bubble; it lives in our world, which is why it's so fascinating to find out that its genes are evolving more slowly than ours," she said.