The genetic clock — mitochondrial Eve and the molecular record

Mitochondrial DNA passes only mother to child and never recombines, so it is a clean maternal lineage; the Y chromosome does the same for fathers. Mutations accumulate at a roughly steady rate, so counting the differences DATES the common ancestor — 'Mitochondrial Eve' (the most-recent common maternal ancestor, ~150-200 kya) and 'Y-chromosomal Adam' (paternal). Sealed: the human mtDNA genome is 16,569 bp (~4 KB), and two lineages coalesce in ~2N generations (https://narrowhighway.com/s/222afa501ad9a65a6cbb50011690b7b5363cc002934bf367eac99bf946b5774b). Honest: Eve and Adam are the most-recent common ancestors of surviving lineages, not necessarily the first humans — yet all maternal lines converging on one woman and all paternal on one man is real and striking (the names were not chosen idly). Haplogroups chart the branches; ancient DNA now reads them straight from bone. The genetic clock traces the peopling of the earth back toward one source. RESONANCE with the linguistic clock; signpost.