After 14 days, is an embryo more than just a ball of cells?

Even before we could experiment on human embryos, we’ve gone back and forth about where we should draw the line: When does an embryo stop being a bunch of cells and start to become a person? If you were Dante Alighieri, writing in the 14th century, you would have drawn the line at the point of “ensoulment.” If you’re a scientist working in the 21st century, you might end experiments at a point called “individuation.” If you are a bioethicist trying to write policy, you might do so after 14 days …

Bioethicists in Europe [have] argued in EMBO Molecular Medicine that it’s time to rethink the timeline of personhood... deciding on where to draw this line is crucial to navigating the ethics of embryonic research. The “14-day rule”, made official in 1985, functions as a drop-dead zone for embryonic research because after 14 days, things start to change in the embryo. Cells no longer simply copy and paste themselves and start to differentiate into three layers known as “the primitive streak,” ...

Has the time has come to extend the 14-day rule to 28 days and probe a bit further into what some researchers call the “black box” of human development? Read more.