Y chromosome passes intact from father to son without recombination. Paternal haplogroups define shared ancient male ancestors. All living men descend from Y-chromosomal Adam in Africa. Haplogroups emerged as humans migrated from Africa to Eurasia and Americas. Y-DNA preserves record of paternal survival over 200,000 years. Autosomal DNA mixes widely but Y-DNA follows single direct path. Haplogroups link to ancient migrations, adaptations, and conquests. Farming spread specific paternal lineages across Europe and Asia. Females cannot test Y-DNA directly – need male paternal relative. Y-DNA analysis uses ISOGG tree and molecular clock for precise timelines. Haplogroup distributions map modern populations sharing ancient lineages. Y-DNA complements but does not replace autosomal or mtDNA ancestry. AncestryDNA and MyHeritage stopped providing Y-DNA data after January 2026. Dedicated Y-tests needed from providers like FamilyTreeDNA or 23andMe. Y-DNA reveals lineage history, not full ancestry or health info.