Indigenous American Genome Reveals Complex History and Unique Diversity

The study identifies over one million previously unreported genetic variants, highlighting the underrepresentation of Indigenous Americans in genomic research.

Evidence suggests at least three major dispersals into South America, including a newly discovered migration from Mesoamerica around 1,300 years ago. Why this matters: This challenges the idea of a simple, single-wave migration model.

The research confirms a genetic connection to Australasian populations, suggesting an ancient admixture event. Why this matters: This supports the theory of an unsampled Asian population (Ypykuéra) contributing to Indigenous American ancestry.

Natural selection has shaped genes related to immunity, metabolism, reproduction, and development, reflecting adaptation to diverse American environments.

European colonization caused a severe genetic bottleneck, decimating Indigenous populations and reducing genetic diversity.

Genetic Diversity:: The study identified 1,426,511 new single-nucleotide variants (SNVs), demonstrating substantial genetic variation within Indigenous American populations. This underscores the need for broader inclusion in genomic resources to improve evolutionary and biomedical inferences.

Population Structure:: Principal component analysis (PCA) reveals clear genetic differentiation between North and South America, with substructure within regions. Genetic similarity mirrors geography, with four principal South American genetic clusters identified: Southern Cone, Eastern South America, Western South America, and Chaco.

Continental Dispersals:: The analysis supports at least three main dispersals into South America:

The earliest dispersal includes individuals older than 9,000 years.

A second dispersal occurred around 9,000 years ago, spreading through Central America into southern Mexico, Belize, Panama, and the Caribbean.

A third dispersal, previously unrecognized, occurred approximately 1,300 years ago, with populations moving from Mesoamerica to South America and the Caribbean.

Australasian Affinity:: Some Indigenous American populations show elevated genetic affinity to present-day Australasians, suggesting admixture with an unsampled ancient Asian population (Ypykuéra).

Archaic Introgression:: The study confirms the presence of archaic hominid DNA (Neanderthals and Denisovans) in Indigenous American genomes. These introgressed variants contributed to adaptation to the American continent, particularly in genes related to immunity, metabolism, and epidermal integrity.

The research highlights the importance of including diverse populations in genomic studies to gain a more complete understanding of human evolution and health.

The findings provide valuable insights into the genetic adaptations of Indigenous Americans to various environments, which can inform future biomedical research.

Q: What is the significance of identifying over a million new genetic variants?

Q: What are the implications of the three identified dispersals into South America?

Q: How did European colonization impact the genetic diversity of Indigenous Americans?