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Studies on human embryonic stem cells are highly controversial, and the current law
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says that embryos must be destroyed after 14-days. But why 14-days? What’s so significant
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about the two week limit, and should we even keep using it?
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Hi there my science buddies. Julian here for DNews. Human embryonic stem cells are one
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of the most legally and morally contentious areas of study. On the one hand, stem cells,
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both adult and embryonic, are valuable for researching a huge range of illnesses and
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diseases, from cancer to diabetes to Alzheimer’s. On the other hand, many people believe that
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this benefit to medicine comes at the cost of potential human lives. If you want a bit
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of background on the moral and medical controversy surrounding stem cells, you can check out
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either of these videos on screen.
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Originally, the 14-day limit comes from a 1979 United States Department of Health, Education,
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and Welfare report. A committee of theologians, psychologists, and doctors came to a compromise:
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human embryonic stem cells could be studied for two weeks after fertilization, beyond
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which time the cells would have to be destroyed. But this limit was fairly arbitrary, as at
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the time, scientists could not keep embryos alive in vitro for more than a few days.
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A later report, organized in 1984 by British existential philosopher Mary Warnock, justified
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the two week limit. The report states that on the 14th or 15th day, a faint line of cells
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appears on the embryo, called the “primitive streak”. This, it was argued, is a moment
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that signifies that the embryo has become an individual being, as before this time the
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embryo could potentially split into twin organisms.
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One of the reasons this stage appealed to those who objected on moral grounds, was that
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if an embryo could split into two people, then it could not yet be an individual person.
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The rule codified an easy to measure mark, coupled with an unambiguous time frame; making
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the question less about conception or “a soul”, while still allowing for a religious
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and moral compromise.
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Additionally, a 2002 report from California stated that less than half of all fertilized
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embryos, both in vitro and in vivo, ever reach the primitive streak, meaning that most of
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embryos used for research would have been unlikely to make it to term anyway..
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But recent advances have made it possible for scientists to keep embryos alive for longer
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than two weeks, by simulating womb-like conditions. With the potential for further research using
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stem cells, the question has been forced again: is the 14-day limit still valid?
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Some scientists say no. Arguing that they could use the research in preventing miscarriages,
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infertility, and birth defects which they believe to be more important than a more or
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less arbitrary time limit. For example, in 2014, researchers were able to cure “induced
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Parkinson's disease” in rats Neuroscientists used human embryonic stem cells to create
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neurons that produce dopamine, which is missing in those who suffer from the disease. Although
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no human clinical trials have been done, these early results with animals have been very
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promising.
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That said, other researchers in bioethics have pointed out that even an arbitrary limit
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is better than no limit at all. As more restrictions are lifted, the very real question becomes
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“where is the limit on human experimentation in the pursuit of knowledge?”