Stammbaum was his word, a stem tree, a family tree, upon which every branch and twig represented a form of life evolved by natural selection from some other form of life—every form except, possibly, the very first and simplest. (He was still undecided, or anyway ambiguous in public, about whether life began from an act of God or a chemical accident. Later, he would opt for the latter.) And he made explicit what Darwin had hinted in The Origin: that this evolutionary process, this tree, included humans.
