Common ancestry, common culture, common environment — all these factors contribute to the genomes of individuals of the same ethnic groups.
Now, for the first time, researchers say they have quantified the non-genetic aspects of race and identity for individuals of the same ethnic group.
In a study published in the academic journal eLife, researchers examined DNA methylation — fingerprints of DNA that can be inherited or altered by life experience and shape how our genes are expressed —among 573 Mexican and Puerto Rican children. DNA methylation reflects individual circumstances — for instance, PTSD stemming from traumatic experiences, air pollution from environmental conditions, after effects from maternal smoking, etc.
They identified 916 differences in methylation associated with Mexican or Puerto Rican ethnicity. Looking at that pool, the researchers identified that only three-quarters of the differences between the two ethnic groups could be explained by genetic ancestry.
This led the researchers to theorize that a large fraction, one quarter, of the DNA fingerprints likely reflect biological signatures of environmental, social or cultural differences between the ethnic groups.
Different racial and ethnic groups tend to follow different diets, live in neighborhoods with varying levels of poverty and pollution, and are more or less likely to smoke. DNA methylation can reflect these subtle cultural and environmental differences.