According to new assimilation theory, assimilation can entail not only the adoption, by immigrants, of the established population's cultural practices, but also the adoption, by the established population, of immigrants' cultural practices. However, empirical research on assimilation has either neglected adaptation on the part of the established population or identified only modest changes. We examine reactions to a massive and rapid inflow of immigrants, and specifically, those of Mexican-origin Californios around the time of the Gold Rush of 1849. Treating naming patterns as indicators of assimilation, we find that Mexican American children born in California after 1849–––and especially boys–––were significantly less likely to receive distinctively Hispanic first names. As a placebo test, we further show that a similar pattern does not obtain in areas (e.g. New Mexico) that did not experience a rapid inflow of new American settlers. The findings validate an important insight of new assimilation theory, as well as shed new light on contemporary research on demographic change.
