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 the “primitive 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 cure “induced

Parkinson's disease” in 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?”