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> > But most pro-life activists use ideas like "DNA deines an organism" and "conception is the first creation of an new DNA code" to support the idea that conception is the beginning of human personhood, which is all very well and good except it doesn't jibe with intuitive definitions of what human personhood is about. . . . I personally have found that to me the definition of human personhood that makes the most sense defines a person as an individual capable of thoughts or at least brain activity.
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> That's an interesting definition, but like most definitions that attempt to draw a line between fetushood and babyhood, it's very vague. Exactly how could a doctor go about determining whether or not a fetus is thinking? So, I urge you to consider this: when a sperm enters an egg, something happens which I can't comprehend and the DNA from both gametes converge to become one. This creates a set of DNA which will never, ever be made again. So, right there, you have a very unique and extremely individual person.
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You're right, of course, except it's not necessarily an "indivudal" person. It can end up being two people, three people, or even eight or nine people (see another post on this topic about a woman bearing octuplets).

And, technically, that set of DNA will be made over and over again trillions upon trillions of times through that individual's lifetime, as the cells replicate. It's just that DNA combination that is highly unlikely to be made again (though, of course, like anything highly unlikely it *could* happen).

There isn't anything exactly magical about meiosis, or at least nothing more magical than any other process of life. We don't understand all the details, true, but then we don't understand all the details of mitosis, either (the fact that your cuts heal is, from one point of view, just as or more miraculous than the fact that you were conceived from a mother and a father). The process is complex but the end result is 23+23=46.

And that DNA combination does not necessarily stay constant throughout the individual's lifetime. The replication of DNA in mitosis is not always perfect; mistakes happen, errors occur, we get mutations. Usually mutant cells die out or the mutation is too small to make a difference; sometimes the mutation is critical and you get cancer; sometimes it's in between and your kids have blue eyes rather than brown. There is even a theory that the long-term buildup of defects in DNA replication is what causes aging.

Okay, sure, the DNA in *all* of your cells doesn't change, but it changes in some of your cells, and who's to say which cell randomly chosen from your body has your "real" DNA? What ends up happening is that as long as the cells are close enough to each other to work reasonably well together, they will, and no one will be the wiser as to which DNA is which. (This is why organ transplants between close genetic matches can work without having to suppress the immune system.) The only mutations that matter in the long run are those of sperm and eggs, since your offspring will grow from a single one of those and any errors will be multiplied a trillionfold, but none of those have any effect on *you*. *You* may be heavily mutated from your original DNA at conception if you've been exposed to radiation or certain chemicals regularly and not even know. Certainly you wouldn't be a different person, even if the mutation were quite a severe one.

Of course in the past we weren't sure when brainwave activity started (though even early dissections showed that the brain itself didn't start forming until a few weeks into pregnancy), but later studies showed a fairly definite cut-off point for detectable brainwaves in a fetus. (We can measure brainwave activity using EEGs, the same way we do with an adult; the electrical pulses produce resonances in magnetic fields, allowing us to measure the presence of pulses in large numbers. Please forgive me if I mangled that technical description. :) But our knowledge of when the brain begins working is based on scientific observations, not on hypotheses.) Brainwaves at the "thinking" level (there are vague and inconclusive cases of detecting brain activity earlier than this, but not at any strength and not at the level of even an unconscious adult human) don't show up until the cerebral cortex forms, somewhere in the sixth month of pregnancy. To be safe, I still don't support abortion of any fetus past the first trimester, when the fetus first starts forming from the embryo.

> > After all, an ovum, in its own way a potential person, dies every menstrual period; millions of spermatazoa, all potential people, die every time a man ejaculates.
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> Well...no. You'd need a complete set of human DNA for a "potential person".

A potential person in a sense. Just like the hamburger I ate recently may be a potential person, since for all I know its proteins may go into the synthesis of sperm cells in my body and for all I know that sperm might father a child in the next few weeks, though that would require a quite horribly unlikely chain of events. Do those proteins then have legal rights?

Of course that argument is ridiculous and stupid, and no one would seriously argue for the rights of the sperm or rights of the ovum. But I'm trying to make a point that there has to be a standard for when a human life begins; for some people, that standard is meiosis and the formation of a new DNA code; for others, it's the beginning of brainwave activity. The trick is deciding which standard we, as a nation, will follow, and to me the one that seems most nearly correct is the one based on brainwave activity.

Ar"guing is fun, but I really am getting worried about those riots :)"thur