From material culture evidence dating as early as 7500 cal BC, it has been established that populations from the interfluvic coast in northern Chile adapted to a maritime economic livelihood. During the 2nd millennium BC, local populations began to experience major social changes arising mainly from an increase in contacts with agropastoral populations from the highlands of the Andes. New radiocarbon data and stable isotope (δ15Ncol, δ13Ccol, and δ13Cap) analyses of human bone remains from interfluvic coastal individuals were obtained. The data showed that these individuals, at the time of contact with highland populations, maintained a mode of subsistence relying principally on marine protein. This suggests that, although instances of social change may have arisen, the livelihoods linked to the consumption of marine resources would have remained constant, demonstrating a high degree of resistance in changing local lifestyles.