London: Now, one of the oldest fish on the planet could help scientists to explain how humans arms and legs were developed.
Researchers at San Francisco State University have found that the American paddle fish, one of the oldest fish on the planet with a giant snout and eggs harvested for caviar, could explain how humans developed arms and legs, the `Daily Mail` reported.
Scientists found the fish duplicated its entire genome about 42 million years ago, according to a new study published in the journal Genome Biology and Evolution.
The study found the unique trait could help explain how fins eventually evolved.
"We found that paddle-fish have had their own genome duplication," assistant professor of biology Karen Crow was quoted as saying by the paper.
"This creates extra genetic material that adds complexity to comparative studies. It may change the way we interpret studies on limb development," Crow said.
In order to study how human limbs develop, scientists compare the limb-building genes found in mice with fin-building genes found in fishes.
The researchers sequenced chromosomal regions containing 19 Hox genes in the American paddle-fish. Hox genes determine body shape and limb development, and have become prime candidates for detecting whole genome duplications.
Whole genome duplications are described as `game-changing events` in evolutionary history that give rise to new species or novel features within a species, the study claims.
They occur when a series of unlikely circumstances coincide, resulting in twin copies of every gene.
When this happens, one scenario that could take place is that one gene in the pair keeps its designated function while the other is either lost or takes on a new purpose.
Previous research on paddle-fish has suggested that fishes possessed the genetic toolkit required to grow limbs long before the evolution of the four-limbed creatures (tetrapods) that developed into reptiles, birds, amphibians and mammals.
Two milestone genome duplications are believed to have taken place before the evolution of jawed vertebrates.