These chunks of DNA are highly informative. For example, we can use their length to date the time of interbreeding. This relies on the fact that over time, long lengths of genome are chopped and swapped by recombination. The longer the intact sequence, the fewer generations undergone since interbreeding—the effect has been confirmed by looking at ancient DNA from Siberian contemporaries of the Neanderthals: modern-looking Homo sapiens sapiens, for whom Neanderthal interbreeding must have been a recent thing. These true Moderns have significantly longer Neanderthal regions in their genome. Such
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