Why are there different Hair Textures?

afro, curly hair, wavy hair, straight hair

For years characteristics that are strongly associated with “blackness” such as thick lips, wide noses, dark skin, and curly or kinky hair were associated with inferiority. These were touted as evidence that these people were closer to lower animals, even considered subhuman, than their often lighter hued counterparts. Today, there seems to be an emerging consciousness or renewed attention to the injustices and inequalities of blacks in America and maybe even around the world. During the 60s civil rights demonstrations were taking place resulting in the Civil Rights Act of 1964 among other progressive measures. The issues of racism and inequality seemed to be unavoidable and one had to acknowledge its existence. The following years seemed different.

“Blacks’ physical features-darker skin, fuller lips and noses   were considered an obvious testament to their inferiority.” – Doing Business with Beauty: Black Women, Hair Salons, and the Racial Enclave Economy by Adia Harvey Wingfield

It seemed like during the 70s and 80s were a time in which blacks “took racial injustices on the chin” and sought to combat racism by excelling while, overall, remaining relatively quiet about any injustices. During the 90s and even into the early 2000s, America experienced a great economic time and on the surface times felt great. Though, in many measures black Americans had seen some improvement (unemployment, college attendance, etc.) under the surface in fact some things had become even worse such as the increased incarceration rate among this group. Now, sometime after the recession, possibly partially attributed to the advent of new technology such as social media, overall growth of the internet, and smartphones, the public is now becoming more aware and vocal about what many scholars have known all along; the state of black America has not come as far from the pre-civil rights era as many had thought.

One minor aspect that has garnered attention is the inherent devaluation of black features. Today, like many other aspects of racism in America, this racism isn’t explicit and many are not even aware of it, but instead it is embedded in culture and society. For example, many black women have been required or have felt the strong need to style their hair in a manner that resembles European hairstyles. This often means using damaging chemicals and tools to straighten the hair which is not how most black women’s hair naturally is. To make one’s hair resemble European women’s hair is to be deemed more attractive and even more professional in the work place. At one point in history, it might have been explicitly expressed that natural black hair is inferior and blacks held little power to fight back against these beliefs. Since then, no one says it outright anymore, instead it is simply accepted.

“However, this systemic racism also gendered in that it intersected with messages about femininity, which stated that women’s worth was directly tied to their physical attractiveness. For black women, systemic racism became gendered; the physical features that were held up as a marker of their racial inferiority also precluded them from achieving dominant ideals of femininity.” – Doing Business with Beauty: Black Women, Hair Salons, and the Racial Enclave Economy by Adia Harvey Wingfield

Black men too have been plagued with conforming to European standards of physical attractiveness when it comes to hair, by wearing low cut hairstyles that draw away attention from the kinkiness of their hair. Men too have used many products that have softened their hair making it look less “ethnic”.

There was a time in the 80s when African Americans expressed pride in their natural hair by sporting afros and using the afro as a symbol of black power. Again, today there is a renewed sense of pride in wearing one’s natural hair. Now sales of hair care products targeted towards straightening “afro-textured” hair have been steadily declining. The natural hair movement gained momentum and continues to grow.

Objectively observing the differences in hair texture among different groups though, I knew this had to be a byproduct of evolution. I wondered what advantages kinky/curly hair or straight hair provided and in what contexts. Or could these changes have been caused by sexual selection. Maybe because the first person/people to have less curly hair or even straight hair was so new and different, this person/people garnered more attention from the opposite sex, therefore resulting in increasingly straighter hair offspring. Maybe there were cultural influences. For example, a culture in Africa believes that people with albinism have magical powers, therefore, this trait is desirable in a mate, and the rate of albinism in this group is much higher than in other populations despite the fact that this trait is in some ways actually detrimental to survival.

I was curious as to what research has been done on the evolution of hair texture and the following is what I have found.

What are the different types of hair texture?

One of the most widely used classification systems of hair texture was created by a man named Andre Walker who also happens to be the hair stylist of the entertainment mogul Oprah Winfrey. Based on Walker’s system there are four broad types of hair texture. The four types 1, 2, 3, and 4 go from the straightest hair to the curliest form. Within each one of those groups are subtypes, a-c.  

What causes hair to have different textures?

Anatomy

The structure that determines the texture is a little part of the scalp called the follicle. Generally, there are two parts of hair: the shaft is the part we see and the follicle is the part that exists below the skin.

Hair Anatomy, Shaft, follicle, bulb, medulla, cortex, sebaceous gland, root sheath, hair matrix, dermal papilla

By OpenStax College/ Wikimedia Commons CC BY 3.0

Starting with the part we see, the shaft is dead. It is made up of proteins called keratin. The shaft is separated into three layers: the medulla (innermost layer), the cortex (the middle layer), and the cuticle (the outermost layer). The cuticle is what most hair care products target. If the shaft is made up of keratin what separates the different layers or is the separation ambiguous?

Next, we have the follicle. The follicle is the living part of the hair which consists of two smaller structures: the papilla and the germinal matrix. The papilla is at the base of the follicle and contains the blood vessels, capillaries, to nourish its cells. The germinal matrix is where new hair cells are produced. Surrounding the papilla and germinal matrix is the bulb which has many different types of stem cells. (I wonder if anyone has attempted to utilize these stem cells for other purposes.) Surrounding the follicle are the inner and outer sheaths that protect and mold the growing hair shaft. Attached to the outer sheath is the arrector pili which is what causes hair to stand up when frightened. The sebaceous gland produces sebum/oil which affects hair’s dryness or lack thereof.

Okay, done with anatomy.

Again, the follicle is the part of the hair that determines hair structure. The cross-sectional shape of the hair determines its texture. The more circular the hair follicle, the straighter the hair is. The flatter the follicle, the curlier hair is. Also, the circular follicle allows more sebum to travel down the hair than a flatter shaft, giving it a shinier look.

Morphologically, the hair follicle of those with curly hair is elliptical in cross-section and the follicle is an asymmetrical S shape, Eurasians have straighter hair shafts and symmetrical hair follicles, straight, and thick hair shafts are common to East Asians. Another interesting piece of information, it is thought that the similar curly hair structure commonly found in Sub-Saharan Africans and Melanesians evolved convergently [1]. This suggests that there was/is some advantage to this type of hair structure. These two groups of people existed independently of one another, but still evolved to have the same hair type, further supporting that there is a useful function of this hair type.

Evolution of Hair Texture

Given that there are different types of hair textures, we would expect there to be different effects on the bearers. Throughout the animal kingdom, common uses for hair include heat insulation, protection, communication, and mating. We don’t know with certainty how the different hair textures in humans emerged, but there is plausible evidence indicating that the different hair textures serve different thermoregulatory purposes. It seems that tightly curled or “kinky” hair emerged in humans as a way to help cool off the scalp in high-temperature environments as is found in Sub-Saharan Africa. The curls of those with kinky air create a layer of space near the scalp that can trap and circulate cool air more easily than those with straight, dense hair.

Nina G. Jablonski is an American anthropologist that studies the evolution of skin color. Though few studies on the effects of hair texture and body temperature have been performed, in a review article published in 2014, Jablonski discusses an experiment that gives credence to the hypothesis that hair texture is important for regulating body temperature. In this study, the experimenters tested how hair style and length affected how much humans sweated. People with shorter and straighter hair sweated less when exposed to high heat [1]. More studies need to be performed to support this hypothesis. It is also important to note that the idea of sexual selection still cannot be excluded from contributing to the formation of different hair textures.

What genes determine hair texture?

Surprisingly, little is known about the genetics of hair structure. We do know a few things, though.

Two genes that are associated with differences in hair thickness in East Asians are the EDAR and FGFR2 genes [2]. The TCHH gene is associated with differences in hair texture in people of northern European ancestry. A review paper by Gillian E. Westgate discusses some more genetic links to hair shape [3]. The gene KRT71 is associated with a curly coat in dogs. Also, certain changes in the gene responsible for the protein Trichohyalin are associated with straighter hair in Europeans. Ever hear of Woolly Hair Syndrome? Woolly hair syndrome is the occurrence of coarse and tightly coiled hair in groups of people that normally do not exhibit this trait. Changes in the gene KRT74 are associated with Woolly Hair Syndrome. Other genetic syndromes such as autosomal recessive hypotrichosis and monilethrix also give potential clues to genes influencing hair texture [2].

Conclusion

There seem to be advantages to having different hair textures depending on the environment. Curly/kinky hair provides better ventilation in hot climates and in cultures that require a lot of physical activity and sweat. Straighter hair seems to provide better insulation in cooler climates. The theory of evolution through natural selection would tell us that those without the most appropriate hair types in their environments died off leaving the better suited individuals to carry on their genes. I wonder though if the thermoregulatory benefits of hair texture were that critical to one’s survival? Wouldn’t someone have thought to shave their hair down if it was too hot or throw something like animal fur on their head if it was too cold?

cat

See, practical and stylish. (katesheets/Flickr CC BY 2.0)

I wonder if sexual selection had a strong contributing effect. Possibly individuals that weren’t as well adapted to the environment just seemed less attractive than their counterparts due to dehydration, a constantly flushed look, or consistent chills. And maybe the woman with the short “do” or the man with a dead raccoon on his head wasn’t quite so appealing either. Maybe it’s more impressive to have a dead boar on the table rather than on your head. Therefore, these people didn’t die early deaths, but instead weren’t chosen as mates.

sexy woman wearing fur hat

No thank you. I prefer women with their natural hair (Crysco Photography/Flickr CC BY-NC-ND 2.0)

 

 

References

  1. Jablonski, N.G. and G. Chaplin, The evolution of skin pigmentation and hair texture in people of African ancestry. Dermatol Clin, 2014. 32(2): p. 113-21.
  2. Shimomura, Y. and A.M. Christiano, Biology and genetics of hair. Annu Rev Genomics Hum Genet, 2010. 11: p. 109-32.
  3. Westgate, G.E., N.V. Botchkareva, and D.J. Tobin, The biology of hair diversity. Int J Cosmet Sci, 2013. 35(4): p. 329-36.

Another good read: How does black hair reflect black history?

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