Bulk and amino acid isotope analyses of hair detail adult diets and infant feeding practices among pre- and post-maize populations of the northern Chilean coast of the Atacama Desert

•Amino acid δ13C analysis of a hair fibre reconstructs infant diet on a monthly basis.•Keratin δ13C alanine value is proposed as a marker of maize consumption.•Marine foodstuffs were a reliable source of protein on the northern coast of Chile.•The introduction of maize had detrimental effects on infant diet and health.