We now know that biological variation among individual humans, while correlated with ancestry, stems from a variety of factors—genetic, environmental, cultural and behavioral. Widespread migration, urbanization and the relaxing of social boundaries over the past century has led to a vast number of people of mixed ancestry.

It is also true that, on average, people whose ancestors lived in the same place tend to be more closely related to one another than people whose ancestors lived in more distant locales. This shared ancestry can be detected based on differences in the frequencies of genetic variants across human populations. So, if the question of race is limited simply to whether our DNA contains information about where our ancestors lived, then genomic science can be said to inform thinking about race. But the history, legacy and meaning of race are more than biogeographic ancestry. The questions underlying the debate are the extent to which differences in characteristics among groups are determined by inheritance, can be shaped by environment and behavior, and are used to defend or attack social policies.

In recent years, we have started to learn about how specific genes contribute to variation in human traits. Commonly varying traits such as body weight and cholesterol levels and diseases like diabetes, cancer and schizophrenia are each influenced by a vast number of genes and by environmental factors.