EMBO Reports 10:4 (April 2009), with Patrick Lee.

If, as we believe, human embryos are human beings who deserve the same basic respect we accord to human beings at later developmental stages, then research that involves deliberately dismembering embryonic humans in order to use their cells for the benefit of others is inherently wrong. Just as harvesting the organs of a living child for the benefit of others is immoral and illegal, so ‘disaggregating’ embryonic human beings would also be immoral and should be illegal—of course governments should therefore not fund such procedures. In this article, we provide some of the evidence that human embryos are indeed human beings and, as such, deserve a level of respect that is incompatible with treating them as disposable research material. We also consider two recent objections to our position.

In sexual reproduction, conception occurs when a sperm cell unites with an oocyte, the two cease to be, and their constituents successfully enter into the makeup of a new and distinct organism, which is called a zygote in its original one-celled stage. This new organism begins to grow by the normal process of differentiated cell division into an embryo, dividing into two cells, then four, eight and so on, although some divisions are asynchronous. Its cells constitute a human organism, for they form a stable body and act together in a coordinated manner, which contributes to regular, predictable and determinate development toward the mature stage of a human being. That is, from the zygote stage onward, the human embryo has within it all of the internal information needed—including chiefly its genetic and epigenetic constitution—and the active disposition to develop itself to the mature stage of a human organism. As long as the embryo is reasonably healthy and is not denied or deprived of a suitable environment and adequate nutrition, it will actively develop itself along the species-specific trajectory of development. This means that the embryo has the same nature—in other words, it is the same kind of entity—from fertilization onward; there is only a difference in degree of maturation, not in kind, between any of the stages from embryo, to fetus, infant and so on. What exists in the early stages of development is not a mere bundle of homogeneous cells. Scientific evidence shows that already at the two-cell stage, and even more so at the four-cell stage and thereafter, there is a difference in the internal structure of the embryonic cells; although they have the same DNA, each has a distinct pattern of gene expression…

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National Institutes of Health