Is Curly Hair Dominant or Recessive?
Curly hair is often described as dominant and straight hair as recessive. That works as a family rule of thumb, but neither label is strictly accurate. Curl is polygenic: many genes each add a little. The best-known straight-hair variant, in the TCHH gene, explains only about 6% of the variation in European hair shape (Medland et al., 2009).
A 2018 meta-analysis of genome-wide studies found 8 new gene regions linked to hair shape, on top of those already known (Liu et al., 2018). The US National Library of Medicine adds that many more genes likely contribute to hair texture (MedlinePlus Genetics). In practice, curl adds up: the more curl-promoting variants you inherit from both parents, the curlier your hair tends to be.
| Hair type | Rule-of-thumb label | What the research shows |
|---|---|---|
| Curly | Dominant | Polygenic and additive. There is no single “curl gene”; many genes contribute. |
| Straight | Recessive | In Europeans, linked to a TCHH variant (rs11803731) that accounts for about 6% of hair-shape variation. |
| Wavy | Neither | An in-between result of the same genes, not a separate trait. About 40% of people of European ancestry have wavy hair, vs 45% straight and 15% curly. |
Is Wavy Hair Dominant or Recessive?
Neither. Wavy hair has no gene of its own. It sits in the middle of the same straight-to-coily spectrum, so it appears when someone inherits a moderate mix of curl-promoting and straight-promoting variants. That is why two wavy parents can have children with straighter or curlier hair than either of them. Wavy hair is also far from rare: in the European-ancestry samples Medland et al. studied, it was almost as common as straight hair (40% vs 45%). For country-by-country figures, see our curly hair prevalence map.
The Punnett square further down this page simplifies the same idea into one gene. Real inheritance runs across many genes at once, which is why curl type within one family can vary so much.
How Hair Genetics Works
Hair genetics decide your hair’s shape, thickness and colour through many genes acting together, not one. For texture, each gene adds a small push toward straighter or curlier hair, which is why the result is a spectrum rather than a set of fixed types. A 2018 analysis of genome-wide studies found 8 new gene regions linked to hair shape on top of those already known (Liu et al., 2018), and the US National Library of Medicine notes that many more genes likely contribute (MedlinePlus Genetics). The table of key genes below shows the best-studied ones.
BY THE NUMBERS
Curly Hair at a Glance
| ~22% of 19,461 people surveyed globally reported curly hair Flament et al., 2025 | 43% Brazil had the highest curly hair prevalence of any country studied in 2025 | 5.5% China had the lowest curly hair prevalence of any country studied in 2025 |
THE BIOLOGY
Why Does Hair Curl at All
The key to your curl pattern is not the hair strand itself. It’s the hair follicle, or the tiny organ inside your scalp that produces each strand. Symmetrical, round follicles produce straight hair. Asymmetrical, oval, or flattened follicles produce wavy or curly hair. The more asymmetrical the follicle, the tighter the curl. As the fiber grows through the follicle, proteins called keratins are laid down unevenly across the cortex of the strand. This phenomenon creates internal tension on one side of the hair strand, making the fiber naturally spiral and bend. A structural protein called trichohyalin plays a central role in cross-linking your curls. Encoded by the TCHH gene, this protein essentially decides the strength and angle of each strand of your hair.
“Hair plays a critical role in enhancing physical appearance, self-esteem, and identity… curl degree varied significantly across age, gender, country and ethnicity.” Flament et al. Clinical, Cosmetic and Investigational Dermatology, February 2025 · 19,461 participants across 9 countriesCurly hair is an additive, polygenetic trait. This means that multiple genes are behind your curly hair, including the hair structure and definition. One’s curliness will depend on how many inherited curl variants across multiple genes.
Key Genes That Shape Your Curl
| GENE | WHAT IT DOES | POPULATION AFFECTED MOST |
| TCHH | Encodes trichohyalin, a protein that cross-links keratin filaments in the follicle’s inner root sheath. The T-allele variant is strongly associated with straight hair in European populations. | Northern & Southern European |
| EDAR | Controls hair shaft thickness and follicle density. The V370A variant produces thick, straight hair one of the strongest signals of positive selection in the Asian genome. | East Asian populations |
| FGFR2 | A fibroblast growth factor receptor involved in follicle development. Polymorphisms linked to hair thickness in East Asian populations, working in concert with EDAR. | East Asian populations |
| PRSS53 | Encodes a serine protease in the inner root sheath. The Q30R variant has been linked to curl variation in South American admixed populations via GWAS. | Admixed Latin American |
| KRT81/86 | Keratin genes that determine structural integrity and shape of the hair fiber. Variants contribute to coil tightness across multiple populations. | Broad — multiple ethnicities |
THE CHART
Curly Hair Genetics by Ethnicity
While curl patterns exist on a spectrum and vary enormously within any ethnic group, population genetics research reveals consistent trends. This is about population-level averages; your curls are always your own.
UNDERSTANDING CURL TYPES
The André Walker Hair Typing System & Ethnicity
The André Walker Hair Typing System is a well-known hair classification scale that ranges from one (1) to four (4). This scale maps fairly well onto genetic ancestry patterns, but it’s not a perfect one-to-one.
| TYPE 1 Straight No curl pattern. Round follicle, symmetrical keratin distribution. Oilier because sebum travels the shaft easily. East Asian · Northern European · Some Native American | TYPE 2 Wavy S-shaped bends. Slightly oval follicle. Ranges from beach wave (2a) to defined waves (2c) with more frizz. Mediterranean · South Asian · Latin American · N. European |
| TYPE 3 Curly Springy, defined S or Z curls. Oval to elliptical follicle. Ranges from loose corkscrew (3a) to tight spirals (3c). Afro-Caribbean · Biracial · Middle Eastern · South Asian · Ashkenazi Jewish | TYPE 4 Coily / Kinky Tight Z-pattern or springy coils. Highly asymmetrical follicle, greatest difference between sides of the cortex. Sub-Saharan African · African American · Afro-Latino |
INHERITANCE
How You Inherit Your Curl Pattern
Curly hair is generally considered a dominant trait, while straight hair is recessive. And since your curl is polygenic (influenced by many genes), the reality is more nuanced than a simple dominant/recessive flip. Think of it like a dimmer switch rather than an on/off button.
| When Both Parents Have Curly Hair → ~90% chance of having children with curly or coily hair → Wavy still possible if both carry recessive straight variants → Curl tightness can vary from either parent’s pattern → Straight from two curly parents is rare — but not impossible | When One Parent is Curly, One Straight → Wavy or curly is the most likely outcome → Curly variants tend to be dominant over straight alleles → Child may have looser curls than the curly parent → Curl genes can re-emerge in grandchildren (skipping a generation) |
A Simplified Punnett Square for Curl Inheritance
‘C’ = curl allele (dominant), ‘s’ = straight allele (recessive). Real curl genetics involves many genes working together in an additive way. Parent 1 (Cs) × Parent 2 (Cs) — Both Wavy/Curly Carriers| C (curl) | s (straight) | ||
| Parent 1 | C (curl) | CC · Curly | Cs · Wavy/Curly |
| s (straight) | Cs · Wavy/Curly | ss · Straight |
BY ETHNICITY
Curly Hair Across Cultures
Let’s go deeper into the curl science behind specific ethnic backgrounds. Keep in mind that ancestry is complex, and most people carry genetic contributions from multiple populations.
African & African-Diaspora Hair
Sub-Saharan African · African American · Afro-Caribbean · Afro-Latino
African hair represents the ancestral norm for all of humanity’s curly hair. It’s our biological default, and straight hair evolved later in other populations.
The tight coils found across Sub-Saharan Africa are produced by highly asymmetrical follicles. The asymmetry also has significant differences between the two sides of the hair cortex. Research shows African hair shape is predominantly curly or kinky, accounting for around 95% of the population studied.
The African diaspora introduces significant genetic diversity. African Americans, Afro-Caribbeans, and Afro-Latinos carry blended ancestry that produces a wide spectrum from 3A to 4C. The hair textures often vary within the same family.
Type 4 hair has the lowest density on the scalp compared to European or Asian hair. Though individual strands tend to be thicker with a unique ribbon-like cross-section.
If you’re working with 4C hair specifically, you need to understand your hair’s porosity level. It’s one of the most useful things you can do for your routine. A nourishing formula like the 100% Virgin Coconut Oil Daily Hydration Conditioner works well for keeping that thickness moisturized daily.
South Asian & Indian Hair
Indian · Pakistani · Bangladeshi · Sri Lankan
South Asian hair sits at a fascinating genetic crossroads, drawing from ancestral North Indian (related to West Eurasian populations) and Dravidian ancestries. This produces an extraordinarily wide range of textures from pin-straight to tight ringlets and everything in between.
High humidity across much of South Asia means that curl patterns will look different from changing climates. Their hair will look wavy in dry conditions and can become full curls in the climate they evolved in,. Many South Asian-descent curlyheads experience this phenomenon when visiting their family’s home country.
If your waves seem to disappear in drier months, why curl patterns change is worth a read. Also, a lightweight formula like the For Curls & Waves Defining Gel can help hold definition through humidity and seasonal changes.
Latin American & Hispanic Hair
Mexican · Brazilian · Colombian · Puerto Rican · Dominican · South Asian
Latin American hair genetics is among the most complex in the world. They reflect centuries of admixture between Indigenous American, European (Spanish and Portuguese), and African populations in varying proportions. These even differ by region and family.
A large GWAS study of 6,630 admixed South American citizens identified three key genes. These genes (EDAR, TCHH, and PRSS53) all contribute to curl variation within this single population.
This genetic diversity means Latino/Hispanic hair spans the entire André Walker spectrum, sometimes dramatically within a single family. There was a multinational hair study in Brazil, one of the most admixed countries on earth. Researchers found that they had the highest curly hair prevalence of any nation studied, at 43%.
Mediterranean & Middle Eastern Hair
Greek · Italian · Lebanese · Egyptian · Turkish · Persian · Arab
Mediterranean and Middle Eastern populations sit genetically between Africa and Northern Europe, and their hair textures reflect this. They had looser strands than the tight coils of Sub-Saharan Africa, but often curlier and darker than Northern European hair.
A study of 120 Arab individuals found 63.4% had textured hair, the highest strand thickness of any studied population. The 2025 Flament study places France, with its significant Mediterranean and North African population, at 21% curly hair prevalence. These findings exactly reflect this genetic middle ground.
East Asian Hair
Chinese · Japanese · Korean · Vietnamese · Thai
East Asian hair is one of the best-studied examples of a genetic adaptation linked to climate. The EDAR gene variant (V370A) which arose roughly 30,000 years ago, produces thicker, straight hair and. It’s considered one of the strongest signatures of positive selection in the human genome.
East Asian hair typically grows fastest (~1.3cm/month), has the largest strand diameter, and shows the highest melanin density. The 2025 multinational study found Japan at 10% and China at 5.5% curly hair prevalence. These two are among the lowest of any countries studied.
EVOLUTION
Where Did Curly Hair Originate?
Curly hair most likely originated in Africa with the earliest modern humans. Tightly curled scalp hair is thought to be the ancestral human hair type, and straighter hair appeared later as populations spread into Europe and East Asia. The leading explanation is heat: in a 2023 study using a thermal manikin, tightly curled hair blocked the most solar heat from reaching the scalp, which reduced the sweating needed to stay cool (Lasisi et al., 2023).
Curly hair is the ancestral default for Homo sapiens. Straight hair evolved independently in two separate genetic lineages — the TCHH mutation in Europe and the EDAR mutation in East Asia. These variations suggest that different climate pressures drove convergent evolution toward straight hair in cold regions. The leading theories are as follows:- straight hair lies flat against the scalp and provides more insulation
- straight hair is oilier, providing better moisture protection in cold, dry air
- tightly coiled hair in tropical climates may have aided thermoregulation by creating a micro-air-layer above the scalp to diffuse solar radiation
YOUR QUESTIONS ANSWERED
Curly Hair Genetics FAQ
Can curly hair skip a generation? Yes. Because curl is polygenic, a person can carry recessive or lower-expression curl variants without expressing them. They can then pass them to a child who, combined with variants from the other parent, expresses curly hair. It’s more common than people think, especially in mixed-ancestry families. Our inheritance diagram above shows exactly how this plays out across three parent combinations. Can my curl pattern change over time? Your DNA doesn’t change, but a number of factors influence the expression of your curly genes, like:- hormones (pregnancy and menopause are major triggers)
- nutrition
- medications
- even hair damage history
