We are each so atomically numerous and so vigorously recycled at death that a significant number of our atoms - up to a billion for each of us, it has been suggested3 - probably once belonged to Shakespeare. A billion more each came from Buddha and Genghis Khan and Beethoven, and any other historical figure you care to name. (The personages have to be historical, apparently, as it takes the atoms some decades to become thoroughly redistributed; however much you may wish it, you are not yet one with Elvis Presley.) So