The new study led by Leopold Eckhart has revealed that origin of hair dates back to an unknown reptile ancestor that lived more than 300 million years ago, in the Paleozoic era.
During the study, the researchers compared the genomes of human, chicken, and green anole lizard.
They discovered six different genes for hair keratin in lizards, the protein from which mammal hair is made.
Moreover, the genes were strongly expressed in the lizard's toes, suggesting that the first hair genes played a role in claw formation.
"At least two of these hair protein keratins are formed in the growth zones of the claws," National Geographic quoted Eckhart, as saying.
Moreover, the chicken genome revealed a single hair gene, however, its unclear what that gene is for, if anything.
The study indicates that modern birds, reptiles, and mammals-as well as dinosaurs-shared an early common ancestor that had claws built from hair keratin.
"Actually, it may be more appropriate to call these proteins claw keratins, which later acquired an additional role in hair," he said.
However, the role of other four hair genes found in lizards is unclear. The scientists believe that they may be related to the growth of scales.
Eckhart believes that hair evolution began with claw keratins that were later adapted to form scales, from which the earliest hairs then developed.
The study is published Proceedings of the National Academy of Sciences.