Background: The justification for Nazi programs involving involuntary euthanasia, forced sterilisation, eugenics and human experimentation were strongly influenced by views about human dignity. The historical development of these views should be examined today because discussions of human worth and value are integral to medical ethics and bioethics. We should learn lessons from how human dignity came to be so distorted to avoid repetition of similar distortions. Discussion: Social Darwinism was foremost amongst the philosophies impacting views of human dignity in the decades leading up to Nazi power in Germany. Charles Darwin's evolutionary theory was quickly applied to human beings and social structure. The term 'survival of the fittest' was coined and seen to be applicable to humans. Belief in the inherent dignity of all humans was rejected by social Darwinists. Influential authors of the day proclaimed that an individual's worth and value were to be determined functionally and materialistically. The popularity of such views ideologically prepared German doctors and nurses to accept Nazi social policies promoting survival of only the fittest humans. A historical survey reveals five general presuppositions that strongly impacted medical ethics in the Nazi era. These same five beliefs are being promoted in different ways in contemporary bioethical discourse. Ethical controversies surrounding human embryos revolve around determinations of their moral status. Economic pressures force individuals and societies to examine whether some people's lives are no longer worth living. Human dignity is again being seen as a relative trait found in certain humans, not something inherent. These views strongly impact what is taken to be acceptable within medical ethics. Summary: Five beliefs central to social Darwinism will be examined in light of their influence on current discussions in medical ethics and bioethics. Acceptance of these during the Nazi era proved destructive to many humans. Their widespread acceptance today would similarly lead to much human death and suffering. A different ethic in needed which views human dignity as inherent to all human individuals.