Abortion, Part 1. The difference between human cells and human persons

Does life begin at conception?

While Catholics have held that view since 1869, Protestants have changed their minds on it a few times — most recently in 1980 when Jerry Falwell started popularizing the idea.

I’m going to do a few posts about abortion since it’s such a politically significant topic, with a lot of complexity. This post will focus on the biology of it all.

Most people, myself included, believe that there is a significance to a human being that is more than our physical bodies. Call it a soul; call it the gift of self-awareness: this is what it means to be not just human but a person.

On a biological level, any bit of us is human. A first-grader’s lost tooth? 100% human. A bit of blood sent off to the lab? Human. Grandpa’s metal knee? Not technically human but it would be inhuman to take it away from him.

A sperm? Half human. An egg? Half human. The two of them together? 100% human.

But is a 100% human cell a person?

When we think about the tooth and blood sample, we know that a 100% human cell isn’t a person. So, based on DNA alone, a zygote (a fertilized egg) is not a person.

Is there some additional quality that would make a zygote a person, though?

What about the fact that it can grow into a human person that we would all recognize? Does the potential of becoming a human person in the future mean that it is a human person now?

I can see three biological issues with that.

First, think of the case of identical twins. At one point they are a single zygote, but that zygote grows into two people. When does the soul part happen? Not at conception, because one zygote didn’t equal one potential person then: it equalled two potential people.

Second, think of the advances of modern medicine. We have cloned many animals from adult cells, and within our lifetimes we’ll face the knowledge that with the right conditions, any cell in our bodies could grow into a new baby.

To that second argument, if you point out that it would require a highly artificial, medically appropriate environment for an adult cell to do that, you’d be right. But now you’re relying on environmental factors to decide whether a human cell is a potential human person, not the condition of its DNA.

Third, most fertilized eggs cannot grow into babies. They don’t implant, they are expelled, and the “mother” is never considered pregnant. Again, the condition of the cell’s DNA is not the deciding factor; the environment decides whether the potential human person will become an actual human person.

Now, I do believe there is some moral significance to the potential of a new mind, a new human life. But it is more like the moral significance of a few notes jotted on paper. It’s sad if it’s never becomes a song, but it’s not a crime.

So what is a good criteria for when human cells become a human person?

I’ll probably write another post on this topic, but briefly: when recognizable brain patterns emerge around week 25 of gestation. That’s how we determine death, and it makes a lot of sense to use the same criteria to determine life.

—The Polite Liberal