How molecular clocks are refining human evolution's timeline

Bridget Alex And Priya Moorjani, The Conversation

In humans, about 36 recombination events occur per generation, one or two per chromosome. The recombination clock, on the other hand, ticks at a rate appropriate for dates within the last 100,000 years. But when geneticists directly measure nucleotide differences between living parents and children (using human pedigrees), the mutation rate is half the other estimate: about 0.5x10⁻⁹ per site per year, or only about three mutations per year. Credit: Bridget Alex, CC BY-ND For the divergence between Neanderthals and modern humans, the slower rate provides an estimate between 765,000-550,000 years ago. Oase’s segments are longer because he had a Neanderthal ancestor just 4–6 generations before he lived, based on estimates using the recombination clock.

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