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Arguments from Observation Chapter 4 Arguments from Observation “It could be human, but the facts suggest otherwise” T urning from the most abstract questions regarding what is and is not logically possible, the present chapter will examine the facts of development in more detail to determine what theory is best supported by them. Given that the notion of zygotic personhood does not involve a fundamental contradiction, the question remains whether this is the most likely scenario. Could it be that some other point in development is a better candidate for when human life and personhood commence? The fact that the augmentative power could, in the abstract, be functioning at the zygotic level does not tell us whether the facts support such a claim. Developmental biology suggests several points that may be indicative of human personhood; the question remains which of these points (if indeed any) marks the beginning of human life. In the following sections, we will consider a related set of arguments for delayed hominization in light of the biological activities observed within the embryo itself. 106 Arguments from Observation 107 Syngamy, Maternally Derived mRNA, and Gene Activation In addition to what we have already seen from Ford, Wallace, and Donceel , there are other arguments claiming that delayed hominization is the best fit with the modern biological facts. Beverly Whelton provides a cross-section of such arguments in support of her position, which she calls “a refinement of immediate hominization from conception to the activation of chromosomal DNA.”1 In her view, the human soul, or substantial form, is present not at the moment of conception (a “moment ” she considers ill-defined, at best), but rather from the moment that the DNA contained in the chromosomes of the embryo begins to drive the activities of development, that is, from the onset of messenger RNA (mRNA) and protein synthesis.2 Note that the claim here is a factual one; the zygote could be human at some point prior, but in fact, it is not. Whelton is attempting to determine when we have evidence for the activity of the augmentative power, not whether such evidence can exist. Although modern scientific evidence has revised or refuted some of Whelton’s specific factual claims, the general structure of her argument remains worthy of consideration . By her account, once the head of the sperm has fused with the membrane of the oocyte (unfertilized egg), the sperm releases its haploid nucleus into the cytoplasm of the egg.3 Subsequently, the maternally derived nucleus completes what is called the “second meiosis,” in which one copy of the maternally derived DNA is discarded and becomes the “second polar body” outside of the zygote. The remaining copy (now called a “pronucleus,” as it is a part of what will eventually be a single 1. B. J. Whelton, “Human Nature, Substantial Change, and Modern Science: Rethinking When a New Human Life Begins,” Proceedings of the American Catholic Philosophical Association 72 (1999): 305–14, at 309. 2. Typically this occurs within eight to twelve hours of sperm-egg fusion. 3. “Haploid” nuclei are found in gametes and contain only one copy of DNA, in contrast to the diploid nuclei found in most other animal cells. Typically, this movement of the spermderived nucleus into the cytoplasm of the zygote occurs within minutes of membrane fusion. See Y. Satouh et al., “Visualization of the Moment of Mouse Sperm-Egg Fusion and Dynamic Localization of IZUMO1,” Journal of Cell Science 125, no. 21 (2012): 4985–90. 108 Arguments from Observation nucleus for a single entity) begins its rendezvous with the pronucleus derived from the sperm. In Whelton’s account, when the pronuclei meet, they “fuse,” and the DNA derived from sperm and egg are intertwined and form the unique arrangement that is characteristic of every new member of an animal species. The intertwining of sperm and egg DNA is known as syngamy and, according to Whelton, is the first time the genome of the new entity is complete and in the arrangement that it will retain throughout the individual’s life. According to Whelton, it is only following syngamy that protein synthesis based on this new genome begins, typically by forty to fifty hours following sperm-egg fusion, at the two- to four-cell stage. This, she asserts, is the first sign of any unique, internally derived activities in the embryo: Although only a single cell at this point [following syngamy, prior to the first cell division], the DNA, RNA, cytoplasmic proteins and...

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Additional Information

ISBN
9780813230245
Related ISBN
9780813230238
MARC Record
OCLC
1038796894
Pages
301
Launched on MUSE
2018-06-13
Language
English
Open Access
No
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