Justin,
One has to wonder if, in all those poor souls that have been denied the right of life, just maybe one of them could have been the discoverer of a cure for any number of illnesses that plague mankind. I guess that question will never be answered.

Or they could have been murderers, thieves or rapists, as cited in Freakonomics by Dubner and Levitt. We'll never know for sure, but they did offer some proof of their position.

The possible life trajectories of new human beings are irrelevant. We wouldn't slaughter newborns based on their statistical likelihood to be criminals, and we wouldn't seek uncontrolled procreation on the principle that we'd have better odds of producing geniuses.

Justin, are you saying there's no difference between a newborn and an embryo?

If you're saying yes, and going to use religion to back your opinion, I'll have to disagree and just say that it's all a part of the major disagreement of when "life" begins.

It would seem that society believes that life begins at birth, as shown by on the 1 year anniversary of a child's exit from the womb, the child is said to be 1 year old. Not 1 year and 9 months old.

When did Moby Dick "begin"? When Melville first began thinking about it? When he first put pen to paper? The first draft? The first edition? Or when the book was rediscovered as a masterpiece, rather than a how-to book on whaling?

Look, it's not a perfect analogy, but as a matter of morality, I see no significant change in a child during the transition from womb to air. Choosing birth as the beginning of a human lifespan is to choose a standard aligned with the scientific understanding of the Dark Ages. As to standards for measuring a life, there's been insufficient advantage to changing traditional starting point for birthdays; we all know that it is preceded by roughly nine months of pre-birth development; that doesn't change the appropriate point to begin driving, drinking, voting, etc.

I know it's convenient to have those months available to poke, prod, and decide the value of that nascent human life to the parents. That doesn't make it moral.

"You know, son, you were the eleventh embryo that we tried and the first without the gene indicating susceptibility to colon cancer. If you'd had it, I'd be playing catch with somebody else right now. Let's go get some ice cream."

While not exactly the same thing, the discussion is a parallel to sometimes when I look at my child that I had with my wife and then think back "what if I'd had a child with one of my exes?" Or when my parents told me of other people they dated before each other, if they'd had a child together, would it have been me?

As for my definition of when life begins, it's when the child can survive outside the womb on its own. So embryo, no. 8 months gestation, yes.

I'd put a newborn baby's odds of surviving "outside the womb on its own" at roughly the same number as an embryo's, which is to say zero.

As for the "what if" with exes, there's a moral gulf between the non-joining of the egg and sperm of a particular adult couple and the cessation of the development of a human being already created.