In the debate about the moral standing of human embryos, some defenders of embryo-destructive research have claimed that human embryos are not human beings until implantation (i.e., when the embryo attaches to the uterus, approximately six days after fertilization), and others have claimed that they are not human beings until gastrulation (i.e., when the possibility of twinning no longer exists and the primitive neural streak first appears, approximately 14 days after fertilization). These claims have been repeated by policymakers, scientists, and bioethicists alike, yet they fly in the face of the embryological evidence. Seeing why will put the embryo research debate on a more solid biological footing.
Life Before Implantation
Over the past few years, Utah Senator Orrin Hatch has pushed aggressively for federal funding of embryo-destructive research. When it comes to abortion, Senator Hatch votes consistently pro-life; he believes we have a moral obligation to protect developing human beings. But he also believes that embryos produced outside of a woman's body, whether by cloning or in vitro fertilization, are not human beings unless or until they are implanted in a uterus. "At the core of my support for regenerative medicine research," he declared in 2002, "is my belief that human life requires and begins in a mother's nurturing womb."
More recently, William Neaves, president of the Stowers Institute for Medical Research in Kansas City, has similarly claimed in public hearings that the embryo does not become a human being until implantation. According to Neaves, not until the embryo receives external, maternal signals at implantation is it able to establish the basic body plan of the human, and only then does it become a self-directing human organism. According to Neaves, these signaling factors somehow transform what was hitherto a mere bundle of cells into a unitary organism.
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