Population descriptors are ways of describing or distinguishing people from each other based on perceived or actual differences. They capture the various ways in which people can differ from one another.

A wide variety of population descriptors are used to describe groups of people in research, healthcare or society. Examples of population descriptors include race, ethnicity, genealogical ancestry, genetic ancestry, indigenous, primary language spoken, nationality, geographic origin, sex at birth, gender identity, disability status and age. Each population descriptor captures a different aspect of a group or individual. One population descriptor is not enough to fully describe or distinguish any individual or group. Depending on the situation, some population descriptors may be more relevant than others.

People commonly use population descriptors and their corresponding categories or numerical scales to describe themselves and others. For example, we use categories like female, male or intersex when referring to biological sex assigned at birth.¹ When referring to age, we use numerical values like months and years. We also use categories like newborn, adolescent or older adult.

Researchers in genomics and healthcare also use population descriptors and corresponding categories to describe who is participating in a research study, what groups are being compared as part of the study and to whom their study findings may apply. Researchers can obtain information about population descriptors in many ways, for instance, by asking participants how they identify, looking in an electronic medical record, using data from a prior research study that was shared, or searching public records. Researchers may also assign a population descriptor to an individual or group using a specific analytical approach, such as using statistics to look at the frequency of DNA variants across the genome.

The definitions, measurement, uses and interpretations of population descriptors have varied over time, across users and around the world. Human rights movements or social and political action can bring about such changes. In addition, new scientific discoveries or knowledge, such as in the fields of genomics, archaeology or social science, can lead to changes. New scientific discoveries along with well-established facts present an opportunity to improve our understanding of human genetic variation, and our understanding of what types of differences between or across groups may be important for health. For example, the first modern humans lived somewhere in Africa approximately 300,000 years ago,² and physical barriers to the migration of humans, such as oceans and mountains, led to geographical differences in the frequency of genetic variants we see within and between populations.³

While we’re often searching for difference, it is important to remember that human beings are far more similar than they are different. When identifying groups that differ genetically, researchers have found that most of the variation occurs within groups of people rather than between them. What this means is that nearly all differences are not specific to a group. Rather, they are sometimes found at different frequencies between groups.

There is not one agreed-upon definition for these terms. The descriptions below highlight key differences across them.

Genetic ancestry

Genetic ancestry refers to the biological relationships between individuals that result from inheriting DNA from common ancestors. These common ancestors are tied to their geographical origins from many centuries ago when long-distance travel was extremely difficult. Parents do not pass down all their DNA to their children, therefore genealogical ancestry and genetic ancestry can be different. Genetic ancestry is based on a statistical measure of genetic similarity across individuals.

Race

People created the concept of race. Race is typically used to divide human populations into groups based on perceived physical appearance (such as skin color), social factors and cultural backgrounds.⁴ Race has been used to inappropriately group people into a hierarchical system to "establish and justify systems of power, privilege, disenfranchisement and oppression." ⁵

Ethnicity

Ethnicity tends to refer to a group of people with shared language, religion, customs, beliefs, heritage and history, even though such attributes are not always confined to a single ethnic group. Ethnicity may also refer to groups that are considered indigenous to an area. Ethnicity is not a biological characteristic.

Methods for estimating genetic ancestry are evolving. To determine an individual’s genetic ancestry, researchers compare DNA variants in that individual to the frequency of those DNA variants in groups of people from around the world who have provided samples of their DNA. These groups of people form what is referred to as "reference populations." Genetic ancestry is estimated using statistical techniques and is typically based on some measure of genetic similarity. An individual with a collection of genetic variants that appear in highest frequency within a reference population is estimated to have ancestors from that reference population. Individuals may have a collection of genetic variants that appear in more than one reference populations, which indicates they likely have ancestors from more than one group. Some have argued that instead of thinking about genetic ancestry as broad groups or categories, genetic ancestry should be considered a continuum.

Currently, genomic researchers do not have DNA samples from many groups of people around the world, which means genetic ancestries for some geographical locations cannot be estimated accurately. In addition, as mentioned above, scientists use reference datasets to calculate ancestries. From one analysis to another, genetic ancestry estimations can be different due to differences in the frequencies of genetic variants in the datasets used. Furthermore, when someone is estimated to have ancestors from more than one group, researchers sometimes lump individuals together into a single group to simplify analyses. Therefore, determining genetic ancestry is a statistical estimate, based on available data, and is not always consistent across studies.

More recently, companies offering ancestry-related services directly to consumers have combined genetic ancestry information with family history information.

Regardless of the outcome of a genetic ancestry test, people will choose how they want to be identified by others. These choices may be informed by DNA, social factors, personal or familial preferences, or lived experiences.

A social construct is an idea or collection of ideas that has been created, agreed upon, accepted, or acknowledged by groups of people in a society. Social constructs offer ways to organize, explain or make sense of the world. Many population descriptors are social constructs.  A socially constructed population descriptor can change over time and be used and defined differently in different parts of the world.⁸

Race and ethnicity are social constructs. There is no clear or consistent way to place people into racial or ethnic groups using biology or innate characteristics. For example, people with similar skin color or hair texture have been defined as different races. Skin color variation has arisen over time from people adapting to varying levels of sun exposure ⁹ and people of similar skin color may have very little in common genetically.

For centuries, definitions of race and ethnicity were overly simplistic, unscientific, unethical and regularly used to support colonialism, slavery, imperialism, scientific racism and eugenics. Race has been used to group people into a hierarchical system that identifies, distinguishes and marginalizes some groups across nations, regions and the world. Race also has been used to “establish and justify systems of power, privilege, disenfranchisement and oppression."⁵

The U.S. federal government notes that the race and ethnicity categories established by the Office of Budget and Management (OMB) are sociopolitical constructs and are not an attempt to define race and ethnicity biologically or genetically. Furthermore, these categories reflect a social definition of race and ethnicity recognized in the U.S. and they do not conform to any biological, anthropological or genetic criteria.¹⁰

While genetic ancestry involves analyzing DNA variants and is tied to biology, as described above, the availability of reference populations can influence the ancestral group(s) a person is categorized into. Scientists must decide what level of resolution they will use to group people and what terms they will use to label these genetic ancestry groups. The categories that result when calculating genetic ancestry are sometimes aligned with social constructs of race and ethnicity. Broad genetic ancestry categories are sometimes labeled using the continents from where people are believed to have origins or roots, such as African, European, and Asian. In this way, descriptors for race, ethnicity and genetic ancestry are often intertwined and misused. Because of these factors, some have described genetic ancestry as socially constructed, too.¹¹

The categories used to describe racial and ethnic groups around the world vary. Different ways of categorizing race and ethnicity arise from different historical and modern-day experiences. Some of these experiences include colonization, forced and voluntary migration, racial or ethnic stratification and systems of governance. For example, Australia’s census form¹² in 2021 asked residents to indicate whether they are “of Aboriginal or Torres Strait Islander origin” and to indicate their “ancestry” using no more than two categories. Some of the ancestry categories included “English,” “Italian,” “Chinese,” “Maori,” and “Australian South Sea Islander.” There is no mention of “race” on the 2021 form, but it did appear in prior years.¹³  In some countries, language spoken, origins or religion matter more than race or ethnicity. France and Italy are examples of countries that do not include race nor ethnicity in their census. Some have argued that including race and ethnicity on censuses is essential for understanding and addressing inequities or racism.