Why Do Humans Have Less Body Hair Than Other Mammals? First-Of-Its-Kind Study Reveals Mystery

The study is important because the findings could eventually lead to new techniques to recover hair after balding and chemotherapy, or in individuals with disorders that cause hair loss. 

Humans have less hair compared to other mammals, including cats. A new study has revealed why. (Image Source: Getty)

Humans have significantly less body hair compared to other mammals such as orangutans, mice and horses, which are covered with long locks. The reason behind humans being covered with less locks than other mammals had remained a mystery for a long time. A first-of-its-kind study has compared the genetic codes from 62 animals, and provided clues about how humans and some other mammals lost their hair. 

The study, conducted by scientists at University of Utah Health and University of Pittsburgh, was recently published in the journal eLife. According to the study, humans have the genes for a full coat of body hair, but these are disabled due to evolution. The study has described a set of genes and regulatory regions of the genome that seem to be essential for making hair. 

Significance of the study

There are certain mechanisms which are responsible for making hair, and the new study has answered these questions. The study is important because the findings could eventually lead to new techniques to recover hair after balding and chemotherapy, or in individuals with disorders that cause hair loss. 

According to the study, nature has used the same strategy at least nine times in mammals that are associated with different branches of the evolutionary tree. Dolphins, ancestors of rhinos, naked mole rats and other hairless mammals are some animals which deactivated a common set of genes to shed their hair and fur. 

In a statement released by University of Utah Health, Nathan Clark, one of the authors on the paper, said the researchers have used biological diversity to learn about humans' genetics and find out regions of the genome that contribute to something important to people.

What are the benefits of being hairless?

Animals across the animal kingdom have different kinds of hair, ranging from coarse hair on monkeys to soft fur on cats. Although human heads have hair, they are considered hairless because their body hair is less conspicuous. Elephants and moustachioed walruses are some animals with sparse hair. 

A receding hairline is beneficial because without dense hair, elephants cool off more easily in hot climates and walruses glide effortlessly in the water. 

Why certain mammals lost their hair

Amanda Kowalczyk, one of the authors on the paper, found that the hairless mammals analysed have accumulated mutations in many of the same genes, and these include genes that code for keratin and additional elements that build the hair shaft and facilitate hair growth, the statement said. 

The study found that regulatory regions of the genome appear to be equally important, because these genes do not code for structures that make hair but rather influence the process indirectly. The regulatory regions when and where certain genes turn on and how much hair is made. 

The researchers analysed genes in hairless animals that evolved at faster rates compared to their counterparts in hairy animals. 

The researchers developed computational methods to compare hundreds of regions of the genome at once, surveying 19,149 genes and 3,43,598 regulatory regions that were conserved across the dozens of mammalian species analysed. 

Clark said as animals are under evolutionary pressure to lose hair, the genes encoding hair become less important. This is the reason why they speed up the rate of genetic changes that are permitted by natural selection. 

Clark further said that some genetic changes might be responsible for loss of hair, and others could be collateral damage after hair stops growing.