Is straight hair the rarest? An in-depth look at hair type genetics

September 22, 2025 •

3 min read

Genetics play a profound role in determining your physical characteristics, and hair texture is no exception. This leads many to wonder, is straight hair the rarest, or are other types less common across the global population? The answer is more nuanced than you might think and depends heavily on how hair is categorized.

Quick Summary

The rarest hair type is not all straight hair, but rather a specific subtype known as 1A, which is extremely fine and perfectly straight. While some forms of straight hair are common, the most elusive is this particular variation, which lacks any wave or curl, making it unique and difficult to style.

Key Points

Subtype 1A is the Rarest: The rarest hair type is not all straight hair, but specifically subtype 1A, which is extremely fine and perfectly straight.
Straight Hair is Not Always Rare: The broader category of straight hair (Type 1) is quite common, especially the 1B subtype.
Genetics Play a Key Role: Your hair's texture is determined by a complex interplay of multiple genes, not just one.
Porosity and Density Matter: Beyond the curl pattern, your hair's ability to absorb moisture (porosity) and the number of strands (density) also contribute to its unique characteristics.
Diverse Rarity: Other hair types, particularly coily (Type 4), are also very rare depending on the specific subtype and geographic population.
Evolutionary History: Some genetic evidence suggests that straight hair may have evolved from curly hair, making the ancestral form curly.

Understanding the Hair Type Classification System

To determine if straight hair is the rarest, one must first understand the widely-used hair typing system developed by stylist Andre Walker. This system categorizes hair into four main types: straight (Type 1), wavy (Type 2), curly (Type 3), and coily (Type 4), with each category further divided into subtypes (A, B, and C). This granular approach reveals that rarity isn't determined by the broad category, but by the specific subtype.

The Straight Hair Subtypes

Straight hair, or Type 1, is often perceived as common, yet it includes distinct subtypes with varying degrees of rarity. The subcategories are:

Type 1A: This is the finest, thinnest, and straightest of all hair types. It's so straight that it holds very little, if any, curl and can often appear oily due to the ease with which natural scalp oils travel down the hair shaft. This is the rarest of all hair types and is most commonly found in individuals of Asian descent.
Type 1B: This hair type is straight but has more volume and a medium texture. It has some body and can hold a curl more easily than 1A, making it one of the most common hair types globally.
Type 1C: This straight hair is typically coarse, thick, and has a bit more volume. It might have a slight wave, and humidity can often cause it to become frizzy.

Comparing Hair Type Rarity

When you look beyond the Type 1 category, it becomes clearer that while some forms of straight hair are prevalent, others are quite rare. Coily hair (Type 4), for example, is also less common than wavy hair in many populations, highlighting the diversity of hair types around the world.

A Comparative Glance at Hair Types


Hair Type	Characteristics	Rarity	Styling Considerations
Type 1A	Extremely fine, stick-straight, lacks volume.	Rarest	Difficult to hold a curl; can appear oily quickly.
Type 1B	Medium texture, straight with some body.	Most common	Can hold a curl better than 1A; versatile.
Type 1C	Coarse, thick, straight, can have slight waves.	Common	Can be prone to frizz; holds style well.
Type 2 (Wavy)	S-shaped waves, can range from fine to coarse.	Common	Can be styled straight or curly; tends towards frizz.
Type 3 (Curly)	Loosely coiled curls, defined ringlets.	Second most rare	Requires moisture to define curls; prone to frizz.
Type 4 (Coily)	Tight coils, dense zig-zag patterns.	Very rare	Prone to dryness and breakage; requires significant moisture.

The Role of Genetics in Hair Texture

Understanding hair rarity is impossible without considering the genetic factors at play. Hair texture is a polygenic trait, meaning it is influenced by multiple genes. The TCHH gene, for example, has been identified as having a significant effect on hair curliness. While the exact genetic mechanisms are still being researched, it's known that certain alleles (gene variations) are more prevalent in different populations, leading to the observed variations in global hair textures.

Some research suggests that curly hair may have been the ancestral trait in humans, with straight hair emerging later through genetic mutation. This fascinating piece of genetic history underscores why some hair types, like the extremely straight 1A, are so rare today.

Beyond Texture: Hair Porosity and Density

Beyond the texture classification, two other factors play a major role in hair health and appearance: porosity and density. Porosity refers to your hair's ability to absorb and retain moisture, while density refers to the number of individual hair strands on your head. These factors, also influenced by genetics, further differentiate one person's hair from another and contribute to its unique characteristics.

High Porosity: Hair with a high porosity has a more open cuticle, allowing it to absorb moisture quickly but also lose it just as fast. This hair type can benefit from heavier moisturizing products.
Low Porosity: With a tightly closed cuticle, low porosity hair takes longer to absorb moisture but holds onto it well once it's in. Lighter, water-based products are often best.

Conclusion: The Rarity of Subtypes

In conclusion, the assertion that straight hair is the rarest is a simplification. While straight hair as a general category is quite common, the truly rarest hair type is the fine, stick-straight 1A subtype. The diversity of hair texture is a beautiful testament to human genetics, with rarity being a complex interplay of dominant and recessive genes, mutations, and ancestral traits.

For more information on the complexities of genetics and human traits, consider exploring resources from authoritative sources like the National Human Genome Research Institute.

Frequently Asked Questions

No, straight hair as a general category is not the rarest. However, the specific subtype 1A, which is extremely fine and completely straight, is considered the rarest hair type globally.

The rarest hair type is subtype 1A, which is a form of straight hair. Other rare types include certain subtypes of coily (Type 4) hair, though their prevalence can vary greatly by population.

Your hair type is primarily determined by genetics. Your DNA influences the shape of your hair follicles, which in turn determines whether your hair will be straight, wavy, curly, or coily.

The most common hair type is believed to be the 1B subtype of straight hair, which is straight but has some body and volume.

The rarity of 1A hair is linked to genetics and its specific characteristics. It's often associated with individuals of Asian descent and is defined by its incredibly fine, pin-straight texture that is difficult to style.

You may have 1A hair if your hair is very fine, flat, and resistant to holding any form of curl. It also tends to become oily easily because the natural sebum from your scalp can travel down the hair shaft without any curls to slow it down.

Rarity itself does not directly affect hair health. However, the underlying characteristics of the hair type, such as strand diameter and porosity, do influence its needs and how you should care for it to maintain its health and vibrancy.