Atoms, in short, are very abundant. They are also fantastically durable. Because they are so long lived, atoms really get around. Every atom you possess has almost certainly passed through several stars and been part of millions of organisms on its way to becoming you. 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 suggested -- 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 we are all reincarnations -- though short-lived ones.
- A Short History of Nearly Everything, Bill Bryson
ETA Review: 'Most of this paragraph is correct, but because atoms are stripped of their electrons in stars, Bryson should have said, ". . . the nuclei of every atom you possess has most likely passed through several stars . . . " One might be shocked that each of the 6 trillion or so humans on Earth have so many of Shakespeare's atoms in them. However, Jupiter Scientific has done an analysis of this problem and the figure in Bryson's book is probably low: It is likely that each of us has about 200 billion atoms that were once in Shakespeare's body.' (An Estimate of the Number of Shakespeare's Atoms in a Living Human Being)