The measure of a revolutionary technology is the rate at which it reveals surprises, and in this sense, ancient DNA is more revolutionary than any previous scientific technology for studying the past, including radiocarbon dating. A more apt analogy is the seventeenth-century invention of the light microscope, which made it possible to visualize the world of microbes and cells that no one before had even imagined. When a new instrument opens up vistas onto a world that has not previously been explored, everything it shows is new, and everything is a surprise. This is what is happening now with
...more
