In 1998, Edward O. Wilson discussed the biological basis of morality, pointed out that the analysis of its material origins should enable us to fashion a wise ethical consensus, and predicted the dawn of science-based moral reasoning. This article testifies that his prediction was right. Morality, being based on altruism and collaboration, evolved as a socially advantageous biological phenomenon aimed at ensuring the survival of our species, which was structured in small groups at high risk of extinction for the 99.5% of its existence. In the last 0.5%, the advent of agriculture resulted in a demographic explosion that impaired human beings' moral discernment, because the socially detrimental consequences of immoral actions, which had been recognised and condemned promptly in small groups consisting of a few tens of members, were diluted among millions of untouched individuals, thereby becoming less easily recognisable. Nowadays, to test the supposed morality of individual actions and government policies, we should use reason or, in doubtful cases, mathematical modelling to determine their predictable effects on the survival of small theoretical communities. Unless we untenably claim that the unlikelihood of extinction of today's immense societies entitles us to overturn the meaning of morality, all actions and policies that would cause the extinction of small communities should be regarded as indisputably immoral. This article also presents some examples of science-based moral arguments showing the immorality of restrictions and bans on research with human embryonic stem cells and demonstrates that the old concept of the "naturalistic fallacy", which philosophers frequently invoke to dismiss any scientific approach to morality, is no longer tenable, because it increasingly emerges to be a proof of what may well be defined the "philosophical fallacy".