Colonialism, ethnogenesis, and biogeographic ancestry in the US Southwest

Differences between self-perceived biogeographic ancestry and estimates derived from DNA are potentially informative about the formation of ethnic identities in different sociohistorical contexts. Here, we compared self-estimates and DNA-estimates in New Mexico, where notions of shared ancestry and ethnic identity have been shaped by centuries of migration and admixture.

We asked 507 New Mexicans of Spanish-speaking descent (NMS) to list their ethnic identity and to estimate their percentages of European and Native American ancestry. We then compared self-estimates to estimates derived from 291,917 single nucleotide polymorphisms (SNPs), and we examined how differences between the estimates varied by ethnic identity.

Most NMS (94%) predicted that they had non-zero percentages of European and Native American ancestry. Self-estimates and SNP-estimates were positively correlated (r_European  = 0.38, r_{Native-American}  = 0.36, p < 0.001). The correlations belie systematic patterns of underestimation and overestimation based on ethnic identity. NMS with ancestral ties to 20th century immigrants, who identified as Mexican or Mexican American, often underestimated their European ancestry (self-estimate < SNP-estimate) and overestimated their Native American ancestry. The pattern was reversed for NMS who emphasized deep connections to colonial New Mexico and identified as Spanish or Spanish American.

While NMS accurately predicted that they had European and Native American ancestry, they predicted ancestry percentages with only moderate accuracy. Differences between self-estimated and SNP-estimated ancestry were associated with ethnic identities that were shaped by migration to the region over the past 400 years. We connect ethnic identities and patterns of ancestry estimation to resistance to colonial hegemony and discuss the implications of our results for the construction of ethnic identities, now and in the past.