Medical research with human embryonic stem cells, despite its enormous potential to reduce human suffering, is banned in many countries and heavily restricted in others. "Moral reasons" are invoked to justify bans and restrictions on this promising research. Rather surprisingly, while those moral reasons have been extensively discussed and hotly debated in several papers, not a single article on the moral aspects of that research has attempted to answer this fundamental question: What is morality? Considering that a scientifically objective definition of morality is essential to determine whether those moral reasons are justified or groundless, this article focuses on the evolutionary origins of morality and its biological basis. Morality arose as a selectively advantageous product of evolution and preceded all religions and philosophies by millions of years. For the 99% of humankind's evolution, morality was axiomatically aimed at reducing the sufferings of the social members, because pains and afflictions, as expressions of diseases and impairments, tended to hasten the extinction of the small ancestral groups, which characteristically consisted of a few tens of members. Had the therapeutic use of human embryos been available in remote times, our ancestors would have deemed it unquestionably immoral to save amorphous and microscopic agglomerates of insensitive cells representing neither parental nor social investment, at the expense of the lives of the suffering members of their little communities. Unless we venture the untenable thesis that the unlikelihood of extinction of our immense societies entitles us to overturn the meaning of morality, we cannot but conclude that bans and restrictions on research with human embryonic stem cells are patently immoral.