How Hair Types Trace Human Dispersal Out of Africa
In the previous articles, we have explored the biology of hair—how follicles shape curls, how genes control texture, and how tightly coiled hair may have helped early humans keep their cool under the equatorial sun. But hair is not just a record of adaptation. It is also a map.
The hair on your head carries the signature of where your ancestors came from. Not because hair determines ancestry, but because the genetic variants that influence hair texture spread with human populations as they migrated across the globe. Some variants arose in specific places, at specific times, and then traveled with the people who carried them—sometimes offering survival advantages, sometimes just hitching a ride.
This article traces that journey. From the origins of tightly coiled hair in Africa to the spread of the EDAR variant in East Asia, from admixture with Neanderthals to the complex mixing of the modern world, we will follow hair as a marker of human migration.
The Ancestral State: Tightly Coiled Hair in Africa
The weight of evidence suggests that the earliest modern humans, who evolved in Africa approximately 300,000 years ago, had tightly coiled or curly scalp hair . This makes sense from an adaptive perspective. As we saw in Article 2, tightly curled hair provides the best protection against solar radiation, reducing heat gain on the scalp while minimizing the need for water-wasting sweat .
In the hot, sunny environments of equatorial Africa, this was a significant survival advantage. Early humans with tighter curls could stay cooler and better hydrated while hunting and gathering under the intense sun. Over many generations, natural selection favored the genes that produced this hair texture, making tightly coiled hair the ancestral state for our species.
But Africa is not a single environment, and human populations within Africa show considerable variation in hair texture even today. Some African populations have looser curls or wavy hair, reflecting the continent’s immense genetic diversity. Africa is the birthplace of humanity, and African populations have had the longest time to accumulate genetic variation—including variation in hair-related genes.
This diversity is sometimes overlooked in popular discussions of hair types, which often treat “African hair” as a single category. In reality, hair texture varies widely across the continent, from the tight coils of the San people of southern Africa to the looser curls of East African populations to the straighter hair found in some North African groups.
The Out-of-Africa Dispersal
Around 60,000 to 80,000 years ago, small groups of modern humans began migrating out of Africa. They crossed the Sinai Peninsula into the Middle East and then spread eastward along the coastlines of South Asia, eventually reaching Southeast Asia and Australia. Later waves migrated northward into Europe and Central Asia.
As these populations moved into new environments, the selective pressures on their hair began to change. In the weaker sunlight of higher latitudes, the extreme heat-protection benefits of tightly coiled hair became less critical. Other factors—cold protection, sexual selection, genetic drift—began to shape hair variation.
This does not mean that tightly coiled hair disappeared. Many populations outside Africa retained curly or coily hair, particularly those that remained in warmer climates closer to the equator. Indigenous Australians, Melanesians, South Indians, and some Southeast Asian groups have curly or wavy hair, reflecting their ancestral African heritage.
But in populations that migrated to colder, less sunny regions, different hair textures became more common—not necessarily because straight hair offered a specific advantage, but because the intense selective pressure for tightly coiled hair relaxed, allowing other variants to persist and spread.
The EDAR Variant: A Genetic Marker of East Asian Migration
One of the most powerful stories in human hair genetics involves a gene called EDAR (Ectodysplasin A Receptor). A specific variant of this gene, known as EDARV370A, is found in extremely high frequencies in East Asian and Native American populations, but is nearly absent in people of African or European ancestry .
What does this variant do? In simple terms, it makes hair thicker and straighter. The same variant is also associated with an increased number of sweat glands and changes in tooth and breast morphology . It is a classic example of pleiotropy—a single genetic variant affecting multiple seemingly unrelated traits.
When and where did this variant arise? By analyzing DNA from people around the world and running computer simulations of how the variant spread, researchers estimate that EDARV370A arose in central China approximately 30,000 years ago .
The timing is crucial. This was after modern humans had already migrated out of Africa and spread across Asia. The variant appeared in a population living in East Asia—probably in what is now China—and then spread rapidly through neighboring populations.
How do we know it spread rapidly? Because the variant shows a clear signature of positive selection. In population genetics, when a new genetic variant offers a survival advantage, it spreads through a population much faster than would be expected by chance alone. The frequency of EDARV370A increased dramatically, reaching fixation (100% frequency) in some East Asian populations before the peopling of the Americas approximately 10,700 years ago .
What was the advantage? The answer is not yet clear. The variant affects multiple traits: thicker hair, more sweat glands, changes in mammary gland development. Perhaps thicker hair helped with cold protection in northern climates. Perhaps more sweat glands helped with cooling in humid environments. Perhaps the mammary gland changes improved infant survival. It is possible that all of these advantages worked together, making the variant beneficial for multiple reasons .
What is clear is that the variant traveled with the people who carried it. As East Asian populations migrated—northward into Siberia, eastward across the Bering Land Bridge into the Americas—they took the EDARV370A variant with them. This is why Native American populations, who descended from these migrants, also have high frequencies of the variant.
TCHH and the Genetics of European Hair
While EDAR tells the story of hair evolution in East Asia, a different gene takes center stage in Europe. That gene is TCHH (Trichohyalin), which encodes a protein produced in the inner root sheath of the hair follicle—the rigid “mold” that shapes the developing hair fiber .
A large genome-wide association study published in 2009 analyzed hair shape in over 5,000 people of European descent. The researchers found that common variants in the TCHH gene were strongly associated with hair curliness—specifically, with straighter hair . The most significant variant, rs11803731, accounts for approximately 6% of the variation in hair shape in European populations.
The variant associated with straighter hair is most common in Northern Europeans and reaches its lowest frequency in Southern European populations like Italians and Spaniards. This geographic pattern parallels the distribution of the EDAR variant in Asia—in both cases, a variant that promotes straighter hair is common where it is cold, and rarer where it is warm.
Unlike EDAR, however, the selective pressure on TCHH is less clear. The variant does not show the same unmistakable signature of recent positive selection that EDAR does . It may have spread through a combination of weak selection (perhaps for cold adaptation) and genetic drift.
Africa’s Hidden Diversity: The Continent of Firsts
One of the most important lessons from human genetics is that Africa is the most genetically diverse continent on Earth. Humans have lived in Africa longer than anywhere else, and over those hundreds of thousands of years, they have accumulated more genetic variation than populations that migrated out of Africa more recently.
This includes variation in hair-related genes. While popular discussions sometimes treat “African hair” as a single category, the reality is far more complex. African populations show a wide range of hair textures, from tightly coiled to wavy to (in some North African groups) even straight.
Some of this variation reflects adaptation to different local environments within Africa. Others reflect population history, migration, and genetic drift. And some reflects the fact that Africa is not a single population but a continent of thousands of distinct ethnic groups, each with its own unique genetic heritage.
Scientists are still working to understand this diversity. Most genetic studies of hair have focused on populations of European or East Asian ancestry, meaning that many relevant genetic variants in African populations may have been missed simply because researchers have not looked in diverse enough populations .
Hair Shape and Cross-Sectional Morphology
Beyond curl pattern, human hair varies in other measurable ways that correlate with geographic ancestry. Studies examining hair cross-sections have found consistent patterns:
| Population | Cross-Sectional Shape | Ellipticity | Characteristics |
|---|---|---|---|
| East Asian | Round | Closest to 1.0 | Largest diameter, thickest fibers |
| European | Oval | Intermediate | Medium diameter |
| African | Elliptical/Flattened | Highest (often >1.8) | Most variable diameter, thinnest fibers |
The ellipticity of a hair fiber—the ratio of its maximum diameter to its minimum diameter—captures how flattened or oval the hair is in cross-section. East Asian hairs tend to be round (ellipticity close to 1.0), while African hairs tend to be more elliptical (ellipticity often greater than 1.8), and European hairs fall somewhere in between .
But it is important to understand that these are population-level tendencies, not rigid rules. There is considerable overlap among groups. A person of African ancestry can have round hair, and a person of East Asian ancestry can have elliptical hair. The distributions overlap.
Even more importantly, researchers have documented that straight-haired individuals from any population—whether East Asian, European, or African—tend to have rounder hair fibers, while curlier-haired individuals have more elliptical fibers . This suggests that ellipticity is a marker of curl, not of ancestry per se.
The Role of Admixture: Neanderthals, Denisovans, and Modern Humans
The story of human migration is not just about modern humans moving out of Africa. It is also about modern humans encountering other hominin populations—Neanderthals in Europe and Asia, Denisovans in Asia—and interbreeding with them.
Most people of non-African ancestry carry small amounts of Neanderthal DNA in their genomes, typically 1-2%. Some populations in Southeast Asia and Oceania also carry Denisovan DNA.
Could these archaic hominins have contributed genetic variants that affect hair texture? Possibly. Some Neanderthal-derived genetic variants influence skin and hair characteristics in modern humans, including a variant associated with red hair and fair skin. But the major genes influencing hair shape—EDAR and TCHH—appear to be modern human in origin.
The EDARV370A variant, for example, arose approximately 30,000 years ago—long after Neanderthals had largely disappeared (their last populations died out around 40,000 years ago) . This variant is specific to modern humans.
However, the dispersal of modern humans into Europe and Asia did bring them into contact with Neanderthals, and that contact left genetic traces. Some researchers have speculated that admixture with Neanderthals or Denisovans may have contributed to the genetic diversity of hair-related traits in non-African populations, but this remains an active area of research .
The Modern World: Migration and Mixing
Today, the old patterns are breaking down.
People move across the planet in ways that would have been unimaginable to our ancestors. A person of East Asian descent may be born in Europe, a person of African descent in China, a person of European descent in South Africa. The geographic correlations that once linked hair texture to ancestry are becoming weaker with each generation.
This is not a problem. It is not a loss. It is simply the next chapter in the story of human migration.
The same forces that shaped human hair over thousands of generations—migration, mixing, adaptation, chance—are still operating today. The only difference is the speed.
A Note on Classification and Categories
Throughout this article, we have used categories like “African,” “European,” and “East Asian” to describe populations. These categories are useful for understanding broad patterns of human genetic variation, but they are also oversimplifications.
Human genetic variation is continuous, not discrete. There is no sharp line where one population ends and another begins. The genes that influence hair texture—like all human genes—vary gradually across geography, with populations sharing more similarity with their neighbors than with distant groups.
The categories we use to talk about human populations are social and historical constructs, not biological absolutes. They are useful tools for understanding patterns of variation, but they can also obscure the complexity and continuity of human diversity .
This is why researchers increasingly prefer to classify hair by its physical characteristics—curl diameter, curl index, number of waves—rather than by the presumed ancestry of the person it grows from . A hair is curly or straight. It is thick or thin. It has a certain cross-sectional shape. These are measurable facts. Who the person’s ancestors were is a different question entirely.
What This Means for Understanding Your Hair
The hair on your head is not just growing from your scalp. It is carrying the story of where your ancestors came from.
If you have tightly coiled hair, you may share a genetic heritage with the earliest modern humans in Africa—the people who first figured out how to protect their brains from the equatorial sun.
If you have thick, straight hair, you may carry the EDAR variant that arose in central China approximately 30,000 years ago and spread with the people who migrated across Asia and into the Americas.
If you have wavy or curly hair that falls somewhere in between, you are part of the vast middle of human variation—the product of countless migrations, mixtures, and chance events that have shaped our species for hundreds of thousands of years.
But here is the most important thing to remember: your hair does not define your identity. Your ancestry does not determine your worth. The patterns we see in hair texture across populations are the result of history, not hierarchy.
Every curl, every wave, every straight strand tells a story. But the story is about survival, migration, and adaptation—not about superiority or inferiority.
Your ancestors survived. They adapted. They moved. They mixed. And somewhere along the way, the shape of their hair was shaped by the sun, the cold, the wind, and the chance combinations of genes that made them who they were.
That story is written on your head. And it is still being written, every time a child is born to parents from different parts of the world, every time a new genetic variant arises, every time a person moves to a new home under a different sky.
The map is still being drawn. And you are part of it.
References
Kamberov, Y. G., Wang, S., Tan, J., Gerbault, P., Wark, A., Tan, L., … & Sabeti, P. C. (2013). Modeling recent human evolution in mice by expression of a selected EDAR variant. Cell, 152(4), 691-702.
De la Mettrie, R., Saint-Léger, D., Loussouarn, G., Garcel, A. L., Porter, C., & Langaney, A. (2007). Shape variability and classification of human hair: a worldwide approach. Human Biology, 79(3), 265-281.
Medland, S. E., Nyholt, D. R., Painter, J. N., McEvoy, B. P., McRae, A. F., Zhu, G., … & Martin, N. G. (2009). Common variants in the trichohyalin gene are associated with straight hair in Europeans. American Journal of Human Genetics, 85(5), 750-755.
University of Edinburgh. (2021). Exploring the impact of selection at hair colour loci across different human populations. ICQG6 Conference Poster.
Westgate, G. E., Ginger, R. S., & Green, M. R. (2017). The biology and genetics of curly hair. Experimental Dermatology, 26(6), 483-490.
Disclaimer: This article was researched and drafted with the assistance of AI. All sources are real and verifiable. Readers are encouraged to check the references themselves and draw their own conclusions.
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