For example, both humans and chimps have a broken copy of a gene that in other mammals helps make vitamin C.... It's hard to imagine how there could be stronger evidence for common ancestry of chimps and humans.... Despite some remaining puzzles, there's no reason to doubt that Darwin had this point right, that all creatures on earth are biological relatives.
The Edge of Evolution: The Search for the Limits of Darwinism (ed. Simon and Schuster, 2008) - ISBN: 9780743296229