I went to a Catholic high school, where I was taught in religion class that life begins at conception. I don’t remember my teacher getting into the biological details, but we all knew what she meant: Life begins at the moment that an earnest sperm finishes his treacherous swimming odyssey and hits that big, beautiful egg.
That’s what many Christians believe, and it’s also the fundamental idea behind the personhood movement. The website of Personhood USA, a nonprofit Christian ministry, highlights this quote by French geneticist Jérôme Lejeune: “After fertilization has taken place a new human being has come into being. It is no longer a matter of taste or opinion…it is plain experimental evidence. Each individual has a very neat beginning, at conception.”
That’s not a common belief among biologists, however. Scott Gilbert of Swarthmore calls the conception story a “founding myth,” like The Aeneid. As he jokes in a popular lecture, “We are not the progeny of some wimpy sperm — we are the progeny of heroes!”
In reality, conception — or more precisely, fertilization — is not a moment. It’s a process.
After the sperm DNA enters the egg, it takes at least 12 hours for it to find its way to the egg’s DNA. The sperm and egg chromosomes condense in a coordinated dance, with the help of lots of proteins call microtubules, eventually forming a zygote. But a true diploid nucleus — that is, one that contains a full set of chromosomes from each parent — does not exist until the zygote has split into two cells, about two days after the sperm first arrive.
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So is that two-cell stage, then, at day two, when personhood begins?
It could be, if you define personhood on a purely genetic level. I have a hard time doing so, though, because of twins. Identical twins share exactly the same genome, but are obviously not the same person.
Read full, original article: Personhood Week: Conception Is a Process
