Most Indians mix Iranian-related, Steppe-related, and AHG-related ancestries. Iranian farmer ancestry traces to early Neolithic Central Asia common to ANI, ASI, Austro-Asiatics, East Asian-related groups before Steppe arrival. Endogamy caused extensive homozygosity and IBD sharing across India. Indians average 29 cM HBD segments, far exceeding Europeans, East Asians, Africans. South Indians show highest homozygosity from consanguinity and founder events. 51% of Indians share IBD with 3rd-degree cousin or closer. AHG ancestry highest in South, Dravidian speakers, Scheduled Castes, Tribes, OBC. Indians carry 1-2% archaic ancestry, reconstructing 1.5 Gb Neanderthal and 0.6 Gb Denisovan introgressed genomes. Indians have largest worldwide Neanderthal ancestry variation and most population-specific Neanderthal segments. 90.7% of worldwide Neanderthal sequences present in Indians. 51% Denisovan sequence unique to Indians. Archaic ancestry correlates positively with AHG proportion. No evidence for pre-50,000-year Out-of-Africa ancestry contribution to modern Indians. Minimum coalescence to sub-Saharan Africans at 54,000 years ago. High archaic frequency regions enrich immune pathways. Neanderthal haplotypes link to COVID susceptibility higher in East India. Founder events elevate homozygous deleterious variants and recessive disease risk.