When it comes to genetics, few features spark as much curiosity as hair type. Among the most debated questions is whether curly hair is dominant. It’s a simple question that opens up a fascinating discussion about inheritance, biology, and human diversity. If you’ve ever looked at your family and wondered why some members have curly hair and others don’t, the answer lies in your genes—but it’s not as straightforward as you might think.
Let’s dive into the science of curly hair, bust a few myths, and understand how your hair texture is shaped by a complex mix of genetic factors.
What Determines Hair Type?
Hair texture is mainly controlled by the shape of the hair follicle. A round follicle produces straight hair, while an oval or kidney-shaped follicle results in curly or wavy hair. But this follicle shape is determined by genes inherited from both your parents.
The structure of the hair shaft also plays a role. In straight hair, the shaft is symmetrical and even. In curly hair, the shaft is asymmetrical and often twists as it grows. These traits are encoded in your DNA and passed down through generations.
However, there isn’t just one single “curly hair gene.” Instead, hair texture is considered a polygenic trait—meaning multiple genes interact to determine the final result.
Understanding Dominance in Genetics
To answer whether curly hair is dominant, we need to understand what “dominant” actually means in genetics.
In basic Mendelian genetics, traits are categorized as either dominant or recessive. A dominant gene will “win out” over a recessive one when both are present. For example, brown eyes are dominant over blue eyes.
But curly hair doesn’t follow this clear-cut pattern. Instead, hair type often shows incomplete dominance. This means that if one parent passes on a gene for straight hair and the other for curly hair, the child may end up with wavy hair—a blend of both.
So, is curly hair dominant? Not entirely. It behaves as an incompletely dominant trait, which means curly hair genes can mix with straight hair genes to produce a middle result.
Curly Hair and Incomplete Dominance
Incomplete dominance explains why many people don’t inherit fully curly or fully straight hair, but rather something in between. If one parent has tight curls and the other has bone-straight hair, their child might end up with loose waves. This blending of traits reflects how multiple genes express themselves simultaneously.
In some cases, curly hair can appear to be dominant in a family if many members have it, but that doesn’t make it genetically dominant in the classic sense. It’s just that the specific combination of genes in that family favors curls more often.
Which Genes Are Involved?
Researchers have identified several genes related to hair texture, with TRICH (trichohyalin) and FGFR2 being two of the most studied.
The TCHH gene, in particular, has been linked to curly hair in people of European descent. A variant of this gene is more frequently found in those with curly or wavy hair. However, scientists have found over 100 genetic variants involved in determining hair shape, many of which interact in unpredictable ways.
Because so many genes are involved, and because they can interact with each other in complex ways, there is no universal gene that guarantees curly hair.
Why Curly Hair Appears Dominant in Some Families
In many families, curly hair seems to “run strong.” You might have curly hair even if only one of your parents does. This can happen due to:
- The expression of dominant gene variants inherited from one parent.
- The influence of multiple curly-hair gene combinations coming together.
- The presence of genetic markers in both parents, even if not visibly expressed.
In these situations, the curly hair gene may simply be more expressive or visible, not necessarily dominant by definition.
Ancestry and Hair Type
Genetics also vary across populations. Curly hair is more prevalent in people of African descent, often forming tight coils. In people of European or Latino ancestry, you may see a range of textures from loose curls to ringlets to waves. East Asians typically have straighter hair due to their unique genetic profiles.
Your ancestry plays a big role in determining how likely you are to inherit curly hair. But again, this doesn’t mean the gene is dominant—just that certain variants are more common in certain populations.
Environmental and Hormonal Factors
While genetics lay the foundation, your environment and hormone levels can influence how your hair grows. Many people experience changes in hair texture at different life stages. For instance:
- Puberty may trigger oil production and changes in hair pattern.
- Pregnancy can sometimes make hair curlier or straighter due to hormone fluctuations.
- Aging often causes hair to thin or change texture.
- Chemotherapy or medical conditions can temporarily or permanently alter hair type.
So, even if your DNA suggests a certain texture, real-life experiences can shift how that texture appears over time.
Why You and Your Siblings May Have Different Hair
It’s common for siblings to have different hair types. Since children inherit a random mix of genes from each parent, one child might receive more of the “curly hair” gene variants, while another may get more “straight hair” variants.
Even twins can end up with different hair textures depending on how those genes are activated and expressed. This is another reason it’s hard to say curly hair is dominant—it doesn’t express itself in a uniform or predictable way.
Can You Predict Your Child’s Hair Type?
While it’s tempting to guess a baby’s future hair based on mom and dad’s textures, it’s not so easy. A child with two curly-haired parents is more likely to have curls, but it’s not guaranteed.
Similarly, two straight-haired parents could carry recessive curly-hair genes that combine and show up in their child. Because so many genes are involved, predictions are more about probability than certainty.
Genetic testing companies like 23andMe or AncestryDNA may offer traits analysis that includes hair texture predictions, but these are based on population averages and probability—not a promise.
Common Myths About Curly Hair Genetics
Myth 1: Curly Hair Always Skips a Generation
This myth likely stems from people misunderstanding recessive gene behavior. Curly hair doesn’t skip generations in a patterned way. It may not show up in one generation due to the genetic combination, but it can resurface if both parents pass down the required variants.
Myth 2: Curly Hair Is Always Stronger
Curly hair may look thick or voluminous, but it is often more fragile. Its coiled shape makes it more prone to breakage and dryness. Hair strength is more about protein structure and care than genetic dominance.
Myth 3: You Can Turn Straight Hair into Curly Hair with Products
Products can enhance or define natural curl patterns, but they can’t create curls if your hair is genetically straight. Texture may change due to damage or hormones, but not from shampoo or styling cream.
Final Word: Genetics and the Beauty of Curls
So, is curly hair dominant? The most accurate answer is: not in the traditional sense. Curly hair is influenced by multiple genes and behaves more like an incompletely dominant trait. This means it can blend with straight hair genes to produce wavy textures, or show up in different forms depending on the unique combination of DNA a person inherits.
Curly hair is beautiful, diverse, and complex—just like the genetics behind it. Whether you inherited your curls from a long line of family members or they showed up as a surprise, your hair is a reflection of the unique genetic story written in your DNA.
FAQs about Curly Hair and Genetics
Is curly hair a dominant or recessive trait?
Curly hair is not strictly dominant or recessive. It follows a pattern of incomplete dominance, meaning traits can blend.
Can two straight-haired parents have a curly-haired child?
Yes, if both parents carry recessive genes for curly hair, their child could inherit those and have curls.
Why do some people have wavy hair?
Wavy hair often results from a mix of curly and straight hair genes, showing intermediate expression.
Can your hair texture change over time?
Yes. Hormones, age, medical treatments, and other factors can influence your hair texture as you grow older.
Are curly hair genes more common in certain ethnic groups?
Yes, curly hair genes are more common in some populations, especially among those with African, Middle Eastern, or Mediterranean ancestry.