[...] between us and all other species lies a seemingly unbridgeable gulf that we acknowledge by defining a category called “animals”. It implies that we consider centipedes, chimpanzees, and clams to share decisive features which each othe but not with us, and to lackfeatures restricted to us. [...] A zologist from outer space would immediately classify us as just a third species of chimpanzee, along with the pybmy chimp of Zaire and the common chimp of the rest of tropica Africa.

Molecular genetic studies of the last half-dozen years have shown that we continue to share over 98 percent of our genetic program with the other two chimps.

Szympans i homo sapiens kształtowały się jako gatunki przez około 4 miliony lat. W tym czasie dochodziło do częstej wymiany genetycznej między gatunkami. Proces ten zakończył się około 5 milionów lat temu.