Philosophical inquiries into morality are as old as philosophy, but it may turn out that morality itself is much, much older than that. At least, that is the main thesis of primatologist Frans De Waal, who in this short book based on his Tanner Lectures at Princeton, elaborates on what biologists have been hinting at since Darwin’s (1871) book The Descent of Man and Hamilton’s (1963) studies on the evolution of altruism: morality is yet another allegedly human characteristic that turns out to be built over evolutionary time by natural selection. This sort of intellectual project has historically generated tension between ‘‘the two cultures’’ (Snow 1959), and just a few years ago E. O. Wilson (1998) was predicting an eventual reduction of all humanities to biology by a continuing expansion of sociobiology and evolutionary psychology. It is interesting, therefore, to find in De Waal’s book a clear willingness toward dialog, both on the part of the scientist and by the four philosophers (Robert Wright, Christine Korsgaard, Philip Kitcher and Peter Singer) called upon to comment on the main essay. Indeed, the idea that science can and should inform philosophical debates is becoming rather popular among both scientists and philosophers (e.g., Gibbard 1997; Sober and Wilson 1998; Skyrms 2000; Green et al. 2001; Pigliucci 2003; Clayton and Schloss 2004). That said, there is plenty of room for disagreement, which is of course were things get interesting. De Waal’s objective is two-fold: to make a case for the idea that humans are by nature moral, and to sketch out how such morality could have evolved from simpler building blocks present in our ancestors and our current close relatives. I will first examine De Waal’s case for his two conclusions, then move on to some of the four philosophers’ objections to parts of his thesis, and finally consider the merits and limits of De Waal’s own response to his critics.