Fur is the hallmark of being a mammal. But bald is beautiful to several mammal freaks, including dolphins, mole rats, elephants, and of course humans. Not to mention the handy adaptation.
However, all our ancestors had plenty of fur. We still have the means to be hairy, according to a new study on relatively hairless mammals. These genes seem to have just been turned off.
By hunting down nearly 20,000 coding genes and 350,000 regulatory genes, comparing 62 different mammalian species, University of Pittsburgh geneticist Amanda Kowalczyk and her team have discovered the mechanism behind these fascinating parallel changes.
This reappearance of the trait in unrelated lineages is known as convergent evolution. In case of hairlessness has evolved independently at least nine times along various branches of the mammalian family tree.
The selection pressure caused by this lack of hair is as diverse as the species that have lost their flocs. For elephants, this is a way to lose heat faster; for marine mammals, being more slender means less resistance when moving through the water; and for us, well, there are probably a lot of pressures, including thermoregulation and parasite reduction.
Despite these differences, Kowalczyk and colleagues found that genetic changes in furless species are mainly due to mutations in the same sets of genes.
Many of these genes accumulating mutations were related to the structure of the hair itself, for example genes encoding keratin proteins, sequences that regulate hair development.
“As animals are under evolutionary pressure to lose hair, the genes that code for hair become less important,” explains University of Pittsburgh geneticist Clark Nathan.
“Therefore, they accelerate the rate of genetic change that natural selection allows. Certain genetic changes may be responsible for hair loss. Others may be collateral damage after the hair stops growing.”
While we still retain many of our ancestors’ fur-encoding genes, their regulatory knobs were “turned off” as a result of the accumulation of these mutations.
The team also identified hundreds of new hair-related regulatory genes and several potential new genes encoding hair. These may prove important for those trying to regain lost hair due to disorders or chemotherapy.
“There are quite a number of genes that we know little about,” says Kowalczyk. “We believe they may play a role in hair growth and maintenance.”
The team approach can also be applied to various convergent evolutionary traits. Now they are using their computer method to look at other health conditions.
‘It’s a way to determine the global genetic mechanisms underlying different traits,’ concludes Clark.
This study was published in eLife.