Genetic Diversity and Forensic Efficiency of Autosomal Short Tandem Repeat Markers in Tribal Populations of India: A Comprehensive Review
Abstract
India's tribal communities represent one of the most genetically and linguistically diverse groups of populations in the world, shaped by millennia of geographic isolation, endogamy, and distinct migratory histories. Autosomal short tandem repeat (STR) markers remain the cornerstone of human identification, kinship analysis, and criminal casework, yet the majority of national STR allele-frequency databases are built predominantly from urban and caste-based cohorts, leaving tribal populations comparatively under-represented. This review synthesizes population-genetic and forensic studies of autosomal STR variation among Indian tribal groups published between 2004 and 2025, with particular emphasis on literature from the past five years (2021–2025), spanning the Himalayan and trans-Himalayan, central, eastern and north-eastern, western, and southern regions of India. Reported forensic efficiency parameters — power of discrimination (PD), power of exclusion (PE), polymorphic information content (PIC), matching probability (PM), and typical paternity index (TPI) — are compiled and compared across studies, alongside patterns of Hardy–Weinberg equilibrium, heterozygosity, and inter-tribal genetic distance. The review further examines methodological developments, including commercial multiplex STR kits, next-generation sequencing (NGS)-based STR typing, and open-source statistical tools that have improved the resolution of tribal population genetic studies. Persistent gaps are identified, including small and geographically clustered sample sizes, uneven regional coverage, limited use of expanded CODIS-core loci in tribal cohorts, and the near-absence of tribe-specific allele-frequency databases usable in Indian courts. The review concludes that systematic, adequately powered autosomal STR profiling of under-studied tribal communities is essential to ensure equitable and statistically valid forensic DNA evidence across India's population strata, and outlines priority directions for future research.