Hairless mammals evolved at a faster pace

While most mammals are covered in fur, some have significantly less body hair – including rhinos, elephants, naked mole rats, dolphins, and humans. Until recently, the reasons for this have remained a mystery. To shed more light on this issue, a research team led by the University of Utah and the University of Pittsburgh has now compared the genetic codes of 62 animal species. 

The analysis revealed that a set of genes and regulatory regions of the genome which seem to be essential for producing hair have been disabled during evolution in several mammalian species, particularly in those that evolved at faster rates. 

“We have taken the creative approach of using biological diversity to learn about our own genetics,” said study senior author Nathan Clark, a geneticist at the University of Utah. “This is helping us to pinpoint regions of our genome that contribute to something important to us.”

According to the scientists, being hairless has its own evolutionary benefits. For instance, without dense hair, elephants cool off more easily in hotter climates and walruses glide effortlessly in water.

However, despite these various reasons, the analysis of 19,149 genes and 343,598 regulatory regions that were conserved across dozens of mammalian species suggested that hairless mammals seem to have accumulated mutations in many of the same genes, including those that code for keratin and other elements that facilitate hair growth. In addition, regulatory regions of the genome – which rather than coding directly for structures that produce hair, influence the process indirectly, by guiding when and where specific genes are activated – appear equally important. 

Another major finding of the study was that hairless mammals evolved at faster rates than their hairy counterparts. “As animals are under evolutionary pressure to lose hair, the genes encoding hair become less important. That’s why they speed up the rate of genetic changes that are permitted by natural selection. Some genetic changes might be responsible for loss of hair. Others could be collateral damage after hair stops growing,” Clark explained.

By answering fundamental questions about the mechanisms shaping this rather rare feature in mammals, the scientists hope to find new ways to recover hair after balding or chemotherapy, as well as in people with disorders that cause hair loss.

The study is published in the journal eLife. 

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By Andrei Ionescu, Earth.com Staff Writer

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