Human dignity and bioethics. A critical philosophy approach

Dignity is a concept commonly used in bioethics. However, its uses are diverse, they can even get to incoherency. Therefore, its important a critical explanation of its profound philosophical meaning and implication of the resources for a notion that confusing. They are based on the idealistic and spiritual, religious and metaphysical, concepts implicitly associated to the notion of dignity. When they "sell us" the "Human dignity", they sell us, at the same time, without we can even notice, other values and notions that we might not want: a certain philosophical anthropology with its conception of human's nature or essence, a certain philosophy of nature, a natural right, an essentialist metaphysics, a religion. Some contemporary philosophers, Habermas, Fukuyama, Rorty, Harris, Bostrom, illustrate the diversity of the resources to dignity: there is an onto-theological and metaphysical conception of human dignity, but others consider that it's possible to perfectly respect the individuals and people in an essentialist, evolutionary, open even to progressive transformation, deliberate, and freely agreed perspective of "human nature" understood as an empiric reality, product of Evolution and History.