Scientists at the University of Basel have identified a gene regulatory switch that was key to evolutionary adaption of limbs in ungulates, a category of animals that includes cattle and pigs. “The fossil record shows that all animals with four limbs originally had five toes (digits),” said Carol Wicking of the University of Queensland, who took part in the study. About 55 million years ago, ungulates developed an even number of toes, or in the case of cattle, cloven hooves. The researchers looked at genes that control the development of toes in the embryo and identified an altered genomic region that leads to even numbers of toes.
“We assume that it is the result of progressive evolution, as this switch degenerated in cattle and other even-toed ungulates, while it remained fully functional in some vertebrates such as mice and humans,” said developmental geneticist Rolf Zeller.
The study, Attenuated sensing of SHH by Ptch1 underlies evolution of bovine limbs, was published in the journal Nature.