The Curly Hair Gene: Fact or Fiction?

Over on our CurlTalk forum, there’s been some discussion about whether or not textured hair is a “genetic defect,” and whether or not the so-called “curly hair gene” can be manipulated to produce straight hair. Naturally, we decided to call on some scientists to literally get to the root of this issue.

Is There a Curly Hair Gene

Every physical trait in the human body is influenced by our genes. DNA sequences affect everything from height to skin tone to eye color to hair color and, of course, hair texture. However, none of these mentioned traits are determined by single genes — some characteristics may be determined by hundreds of genes interacting in ways poorly understood by science. Curly hair, like most traits, is the result of a multi-gene interaction.

“Hair form is genetically controlled,” explains professor Erik Trinkaus from Washington University in St. Louis. “But to my knowledge nobody knows what the underlying genetic basis for it might be, and it is likely to be very complex.”

So while there is academic consensus that curly hair is largely genetically determined, there is no single curly hair gene.

The Origin of Curls?

So where do curls, kinks, and waves come from then? Most evolutionary theorists agree that human ancestry can be traced back to Sub-Saharan Africa about 500,000 years ago, but it also appears in other hot, sunny places. I sat down with Kawika Chee, a genetics tutor and genetic research regulatory committee member at the University of Hawaii, to discuss two popular theories for how and why curls helped our ancestors, based on research from Nina Jablonski’s book, “Skin: A Natural History.”

Evolutionary Advantages

1. Sun protection and heat relief: Since humans evolved in the blazing equatorial sunlight of Sub-Saharan Africa, thick, tightly-coiled hair may have offered a sort of natural sunscreen and shade for developing brains and bodies. Also, hair that hangs straight provides an extra layer of heat insulation over the shoulders, neck, and back. In hot climates, this would be harmful to early humans or human ancestors.
2. Preventing obstruction of vision: Before salons and bang trims, straight hair would have thwarted a hunter’s ability to see prey clearly. Tightly coiled hair sits more on top of the head and doesn’t block out one’s field of view.

Then there’s the potential that curls were just pure chance. There are instances in our evolutionary history in which a random, mass extinction of a group of individuals kills off an entire genetic lineage. There may have been a tragedy that wiped out almost everybody, regardless of their hair texture, coincidentally leaving only a tiny group of people who happen to have curly hair. The descendants of these fortunate folks would have passed along curly hair to their offspring and future generations still living today. After all, curly haired folks make up 60 percent of the current world population.

Final Thoughts

• Hair texture has been evolving for thousands upon thousands of years. Variations in hair texture — from coily to straight to kinky to wavy — are caused by evolutionary processes that favored a specific texture according to location, climate or any other host of factors.
• There is no single curly hair gene, and there is no way to genetically alter the presence of curly hair. In fact, medical science isn’t great at altering human genes even in simple, well-understood traits.
• Curly hair is not a defect, as its presence in geographically and ethnically disparate populations all over the world suggests that it certainly has its advantages, evolutionary and otherwise. But we already knew that, didn’t we curlies?