A close reading of Charles Darwin's The Descent of Man reveals that so-called altruistic behavior is not a minor quirk, but it is actually the signature trait that will determine whether the human species continues, or disappears like 99% of the species that have ever existed on planet earth. In fact, Darwin makes clear in Descent that human evolution is long past the time when random physical variations are the make-or-break traits that adjudicate mankind’s survival. Rather, it is higher-level attributes of selfless service and heroism (often enshrined in religion and moral philosophy) that have determined mankind’s most recent evolution and that will be instrumental in mankind’s future survival.