Human hair and its evolution

Curly hair, bushy beard, baldness, straight or blonde hair, etc; there are many options, shapes and quantities but, what is it that determines and makes our hair grow in one way and not in another?

A group of scientists who are part of the Consortium for the Analysis of the Diversity and Evolution of Latin America (CANDELA) detected eighteen genetic variants statistically associated to pilosity craniofacial features. Of those new characteristics, ten were reported for the first time. The study was published in Nature Communications magazine.

“One of these genes, for instance, is the one who determines how wavy our hair will be and the thickness of the eyebrows. These findings are important because they firstly broaden the knowledge we have on hair distribution and pilosity over the genetic base on those characteristics. Furthermore, it strengthens the idea that some selective processes that took place thousands of years ago determined the variation of features – in terms of pilosity – which are common in current humans”, Rolando González-José, CONICET independent researcher at the Patagonian National Research Center (CENPAT-CONICET).

Some genetic and morphological characteristics are related to evolutionary processes that affected men along history, such as the differentiation with other primates as regards pilosity features.

“Classic literature has postulated that the loss of facial and body pilosity corresponds to strong selective processes that have to do with more effective perspiration in connection to bipedal posture. However, it is also true that there is a great variation in pilosity distribution in human populations. So straight hair is absent in Sub-Saharan Africa and the greatest variation in hair is restricted to Western Europe. Other features, like baldness, have uneven distribution between sexes: only men express this external feature”, the researcher affirms.

In order to conduct this study, the scientists collected and analyzed more than 6 thousand samples from volunteers of five Latin American countries (Chile, Colombia, Brazil, Mexico and Peru). Apart from genetic data and phenotypes, the researchers studied the ancestry percentages of the people due to the complex history of miscegenation of the inhabitants of the continent.

“Europeans have straight hair due to the mutation of one genetic variation and it is a different one in the case of the Asians. When they reached America, they hybridized with the native people and the result is like shuffling a deck. This study allowed us to discover variants of other genes directly related to characteristics of hair not known so far”, Virginia Ramallo, CONICET assistant researcher at the CENPAT, comments.

This study has also other potential applications in the future. “For instance, the cosmetics industry has focused classically on products that alter the appearance of keratin fibers in hair once it is out of the follicle, making its shape straight, curly, etc. Our study increases the interest in exploring mechanisms that occur in the early formation of hair, where the genes we detected and studied affect the development inside the follicle itself, before hair comes out”, González-José affirms.

In addition to favorable conditions for the development of hair care products, to know the genetic processes that are involved in hair appearance can be really valuable for justice. “As this database increases, we will be able to infer what is known as forensic prediction of phenotype”, Ramallo states.

Europe with less hair

Baldness is inherent in men because it is associated to one masculine hormone; however it does not happen in the same frequency and way in all populations. This study helped scientists to understand some specific characteristics of our continent linked to hair loss.

“Volunteers who had most American ancestry are less prone to baldness. It is more common in the European population, which is more likely to have these androgen receptors interfere in the cell turnover and maintenance of active hair follicle”, the researcher states.