The Ancestor's Tale: A Pilgrimage to the Dawn of Evolution

by Richard Dawkins

Cold, oxygen-free conditions do somewhat slow DNA’s inexorable decline to illegibility. Currently, the oldest genome on record is from a 700,000-year-old horse bone preserved in Canadian permafrost. Even above freezing, a cool and stable environment can preserve DNA for hundreds of thousands of years. Bones retrieved from excavations in cool caves have provided various quantities of human DNA, most spectacularly the entire genome of a 50,000-year-old incest-spawned Neanderthal (as we shall see). Imagine the kerfuffle if somebody managed to clone her. But long though these timespans are in human terms, they correspond to only a tiny fraction of our journey into the past. Alas, chemistry suggests that the upper limit for retaining recognisable ancient DNA is only a few million years—certainly not enough to reach back to the time of the dinosaurs.