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  • Studies on human embryonic stem cells are highly controversial, and the current law

  • says that embryos must be destroyed after 14-days. But why 14-days? What’s so significant

  • about the two week limit, and should we even keep using it?

  • Hi there my science buddies. Julian here for DNews. Human embryonic stem cells are one

  • of the most legally and morally contentious areas of study. On the one hand, stem cells,

  • both adult and embryonic, are valuable for researching a huge range of illnesses and

  • diseases, from cancer to diabetes to Alzheimer’s. On the other hand, many people believe that

  • this benefit to medicine comes at the cost of potential human lives. If you want a bit

  • of background on the moral and medical controversy surrounding stem cells, you can check out

  • either of these videos on screen.

  • Originally, the 14-day limit comes from a 1979 United States Department of Health, Education,

  • and Welfare report. A committee of theologians, psychologists, and doctors came to a compromise:

  • human embryonic stem cells could be studied for two weeks after fertilization, beyond

  • which time the cells would have to be destroyed. But this limit was fairly arbitrary, as at

  • the time, scientists could not keep embryos alive in vitro for more than a few days.

  • A later report, organized in 1984 by British existential philosopher Mary Warnock, justified

  • the two week limit. The report states that on the 14th or 15th day, a faint line of cells

  • appears on the embryo, called theprimitive streak”. This, it was argued, is a moment

  • that signifies that the embryo has become an individual being, as before this time the

  • embryo could potentially split into twin organisms.

  • One of the reasons this stage appealed to those who objected on moral grounds, was that

  • if an embryo could split into two people, then it could not yet be an individual person.

  • The rule codified an easy to measure mark, coupled with an unambiguous time frame; making

  • the question less about conception or “a soul”, while still allowing for a religious

  • and moral compromise.

  • Additionally, a 2002 report from California stated that less than half of all fertilized

  • embryos, both in vitro and in vivo, ever reach the primitive streak, meaning that most of

  • embryos used for research would have been unlikely to make it to term anyway..

  • But recent advances have made it possible for scientists to keep embryos alive for longer

  • than two weeks, by simulating womb-like conditions. With the potential for further research using

  • stem cells, the question has been forced again: is the 14-day limit still valid?

  • Some scientists say no. Arguing that they could use the research in preventing miscarriages,

  • infertility, and birth defects which they believe to be more important than a more or

  • less arbitrary time limit. For example, in 2014, researchers were able to cureinduced

  • Parkinson's diseasein rats Neuroscientists used human embryonic stem cells to create

  • neurons that produce dopamine, which is missing in those who suffer from the disease. Although

  • no human clinical trials have been done, these early results with animals have been very

  • promising.

  • That said, other researchers in bioethics have pointed out that even an arbitrary limit

  • is better than no limit at all. As more restrictions are lifted, the very real question becomes

  • where is the limit on human experimentation in the pursuit of knowledge?”

Studies on human embryonic stem cells are highly controversial, and the current law

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