Modern science has determined that racial categories do not accurately reflect human biological variation. Humans share 99.9% of their DNA, and the genetic differences that do exist don’t sort neatly into the racial groups societies have constructed. The American Association of Biological Anthropologists put it plainly: “Humans are not divided biologically into distinct continental types or racial genetic clusters.” Race is real as a social and political force, but it is not a meaningful way to classify human biology.
Most Genetic Variation Exists Within Groups, Not Between Them
The single most important finding from modern genetics on this topic is a consistent, well-replicated number: about 85% of all human genetic variation exists within any given population, while only about 15% of variation exists between populations. That means two people from the same racial group can be more genetically different from each other than either is from someone in a completely different racial group. This finding, confirmed repeatedly since it was first reported in the 1970s, fundamentally undermines the idea that racial categories capture distinct biological types.
The Human Genome Project reinforced this picture. When researchers mapped the full human genome, they found that all humans are 99.9% identical at the DNA level. The 0.1% that varies is what accounts for all individual differences in appearance, disease susceptibility, and other traits. But that variation is distributed across humanity in ways that don’t respect racial boundaries.
Traits Change Gradually, Not in Sharp Racial Boundaries
One of the key concepts in understanding why race fails as biology is clinal variation. A cline is a gradual change in a biological trait across a geographic area. Skin color, for example, doesn’t jump abruptly from one shade to another at some border between “races.” It shifts gradually across latitudes, driven by the intensity of ultraviolet radiation in different regions. The same is true for most genetically influenced traits: they change along smooth geographic gradients rather than clustering into discrete racial packages.
Skin color itself is a useful case study. The pigment in darker skin protects against the breakdown of folate, a B vitamin critical for fertility and fetal development. In regions near the equator, where UV radiation is intense, natural selection strongly favored darker skin to conserve folate. Farther from the equator, lighter skin was advantageous because it allowed more UV penetration for vitamin D production. This is a story about geography, sunlight, and specific selective pressures over tens of thousands of years. It has nothing to do with the broad racial categories that societies later invented to classify people.
Even traits we most closely associate with racial identity, like facial features, skin color, and hair type, don’t distribute across our species in a way that maps onto socially recognized racial groups. Different traits follow different geographic gradients independently of one another, which means there’s no point on a map where one “race” cleanly ends and another begins.
Ancestry and Race Are Not the Same Thing
Modern genomics does recognize that people whose ancestors lived in the same geographic region tend to share certain genetic variants. This concept, called biogeographical ancestry, is useful in research and medicine. But geneticists increasingly distinguish it from race. As one medical geneticist explained in a study published in Social Studies of Science: “Race is a social term. It’s applied by people in a society… But that’s not how I phenotype the participants in studies.” What a geneticist needs to know is the actual pattern of genetic variation a person carries, not which racial checkbox they mark on a form.
Some researchers have developed statistical tools specifically to analyze genetic differences without relying on racial categories at all. These tools identify clusters of genetic similarity directly from the data, without imposing social labels. The clusters that emerge sometimes loosely correspond to continental regions, reflecting shared ancestry, but they’re fuzzy, overlapping, and far more complex than a handful of racial groups could capture. No human population has ever been biologically “pure” or truly isolated from neighboring groups. Migration, intermarriage, and gene flow have been constant features of human history.
Race Still Affects Health, Just Not Through Biology
If race isn’t biological, why do health outcomes differ so starkly between racial groups? The answer lies in the social experience of race, not in genetic destiny. Diet, exercise patterns, exposure to environmental toxins, access to healthcare, neighborhood safety, and chronic stress all differ between racial and socioeconomic groups. These factors don’t just affect health in obvious ways. They can actually alter how genes behave.
The field of epigenetics studies changes in gene expression that occur without any change to the DNA sequence itself. Environmental stress, including the kind caused by discrimination, violence, poverty, and trauma, can modify chemical tags on DNA that turn genes up or down. Research has shown that psychosocial stress is associated with changes in DNA methylation, one of the primary mechanisms of epigenetic regulation. These changes can affect stress hormone systems: infants born to mothers who experienced depression or anxiety during pregnancy showed altered regulation of their cortisol response at just three months old.
Animal studies have confirmed that these effects are driven by social environment rather than genetics. In cross-fostering experiments, where offspring were raised by mothers who were not their biological parents, the nurturing behavior of the mother, not the inherited genes, determined the epigenetic changes in the offspring. The social environment literally reshaped gene expression.
Black Americans, on average, experience higher levels of chronic psychosocial stress from sources like discrimination, economic disadvantage, neighborhood violence, and disproportionate incarceration of family members. These stressors can accumulate across a lifetime and even across generations through epigenetic changes, contributing to disparities in conditions like preterm birth, cardiovascular disease, and other health outcomes. The cause is systemic inequity, not racial biology.
Medicine Is Catching Up
For decades, some clinical tools built race directly into their calculations in ways that could harm patients. One prominent example was the formula used to estimate kidney function. The equation included an automatic upward adjustment for Black patients, based on the unfounded assumption that Black people inherently have higher muscle mass than white people. In practice, this made Black patients appear to have better kidney function than they actually did, potentially delaying referrals for treatment and transplant eligibility.
Medical institutions have now begun removing race from these calculations. A race-neutral kidney function equation has been adopted, and similar corrections are being reconsidered across other specialties, including pulmonary function testing. The shift reflects a growing recognition within medicine that using race as a biological proxy introduces bias and can worsen the very disparities it was sometimes intended to account for.
Where the Scientific Consensus Stands
The American Association of Biological Anthropologists issued a formal statement making the discipline’s position explicit: racial categories “do not provide an accurate picture of human biological variation.” The statement traces the Western concept of race to European colonialism, describing it as a classification system that “emerged from, and in support of, European colonialism, oppression, and discrimination” rather than from biological observation. It was never accurate in the past, the statement notes, and it remains inaccurate today.
This doesn’t mean that human biological diversity isn’t real or important. People differ in medically significant ways, and ancestry-related genetic variants matter for understanding disease risk and drug response. But the broad racial categories that societies use, typically a handful of groups defined largely by appearance, are too blunt and too culturally contingent to capture the actual structure of human genetic variation. The science points clearly in one direction: race is a powerful social reality with profound consequences for people’s lives, but it is not a valid framework for dividing humanity into biological types.