"In 1967, American philosopher Dr Mortimer Adler wrote The Difference of Man and the Difference It Makes, in which he raised the question of 'how man differs from other animals'.
"Adler argued that either humans or animals differed 'basically in kind or basically in degree'. Adler believed it to be the former and that the latter could have grave consequences.
"Fifty years later, the first successful human-pig chimera was created by the Salk Institute in California. The name ‘chimera’ originates in Greek mythology. In science it describes a single organism composed of cells from different zygotes."
"In 2004, the President’s Council on Bioethics of the USA published Reproduction and Responsibility: The Regulation of New Biotechnologies whereby the council drew clear boundaries. The council objected to mixing human and non-human embryonic cells, which included the earliest stages of embryological development. It further advised that judging the moral worth of a part-human/part-animal entity would be impossible."
"Adler, correctly, predicted that his assumptions about the primacy of humankind would 'not go unchallenged' and believed his argument would 'be subject to critical scrutiny later, at points where it is more appropriate or feasible to do so.'
"Human-pig chimeras are a remarkable scientific achievement. However, science alone cannot satisfy the question of personhood and moral status. Perhaps then, in the interest of ethics, this success should be followed by revisiting first principles, clarifying guidelines and resetting boundaries."
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