Brazil, the largest Latin American country, is underrepresented in genomic research despite boasting the world’s largest recently admixed population. In this study, we generated 2723 high-coverage whole-genome sequences from the Brazilian population, including urban, rural, and riverine communities representing diverse ethnic backgrounds. We reveal the impressive genomic diversity of Brazilians, identifying >8 million previously unknown variants, including 36,637 predicted deleterious and potentially affecting population health. We found a positive correlation between these deleterious variants and ancestry. Brazilian genomes are a global haplotype mosaic shaped by nonrandom mating, with peak admixture in the 18th and 19th centuries. Within this diversity, ancestry-specific haplotypes exhibit an uneven spatiotemporal distribution. We also identified putatively selected genes in this diverse population, primarily linked to fertility, immune response, and metabolic traits.

Significance: It was previously believed that placental mammals present no variability in oxytocin (OXT). The present study reports novel data on the diversity of OXT and its receptor ( OXTR ) in primate species, including New World monkeys. Contrary to prior expectations, we found three novel OXT forms and several OXTR nonsynonymous changes not previously described. In the Cebidae family, signals of positive selection were found for an OXT variant at position 8, which is associated with larger litter sizes. We detected positive selection for OXTR forms and report a coevolutionary process between changes in OXT and OXTR.