NUNZIUM

Body hair is a defining mammalian characteristic, but several mammals, such as whales, naked mole rats and humans, have notably less hair. The evolutionary mechanism of body hair loss is well understood: some animals do not have hair on their entire body because it is not necessary for survival or reproduction. For example, certain marine mammals, such as dolphins and whales, have little to no body hair because it would harm their ability to swim efficiently. Similarly, some animals that live in hot environments may have less hair as it helps them to regulate their body temperature. It is believed that also humans have evolved to have hairless skin because it allows them to regulate their body temperature. Humans have evolved to have efficient sweat glands, which help them to cool down by sweating. Fur can trap heat and make it difficult for an organism to cool down, which would be detrimental in hot environments. Additionally, the development of clothing and other body coverings has also made fur unnecessary for human survival.

Even though all these facts are known and understood, the genetic mechanism of body hair growth is still a mystery. A recent study by scientists from the University of Utah, published in the journal Elife, unlocked the mystery by examining how hairlessness evolved in different species at different times. By comparing the human genetic code with those of 62 other mammals, including elephants, manatees and chimpanzees, they managed to identify the genes involved in the expression of body hair. To find the genetic basis of reduced hair quantity, the scientists compared more than 19,000 genes and, through cutting-edge methods, narrowed their focus to those linked to keeping or losing body hair. Many genes linked to hair growth contain instructions for making the protein keratin, which forms hair, nails and the skin’s outer layer. The authors found that although the genes for a complete covering of body hair remain in our genetic code, they have been muted and lost their function.

This study marks the first time genetic mechanisms behind various hair traits have been studied in such a diverse group of mammals. Using a novel computational approach, which allows for estimating the genome evolution rate, the research team was able to identify genes and processes that no one knew to be involved in hair growth or hairlessness in mammals. This study and the method used may pave the way for finding out how to treat genetic conditions such as baldness.