Britannica
Sources used in this answer
Why do genetic markers not divide humans into clear biological races?
Created from Britannica articles
using AI.
AI can make mistakes, so verify using Britannica articles.
Race
Skin color is one of the variables that has been used to classify people into different racial categories.
Genetic markers do not divide humans into clear biological races because human biological variation is continuous rather than categorical. While early researchers hoped to identify distinct genetic boundaries between groups, modern science has demonstrated that such divisions are not supported by the evidence.1
Several key factors explain why these markers fail to define biological races:
- Clinal Variation: Most human physical and genetic differences are expressed in subtle gradations (clines) over wide geographic spaces rather than in abrupt, distinct changes.12
- Internal Variation: Genetic studies have consistently shown that internal variation within any given population is greater than the variation between different populations.1
- Independent Inheritance: Phenotypic features—such as skin color, hair texture, and body structure—are inherited independently of one another. Because these traits do not cluster together in a consistent way, they cannot be used to define discrete racial groups.1
- Shared Alleles: While populations may differ in the frequency of certain alleles, these same alleles are typically found across most human groups. There are no significant genetic discontinuities that separate humanity into distinct biological races.3
Ultimately, human physical diversity is best understood as a result of evolutionary adaptation to differing environments, such as variations in sunlight, altitude, and climate.2