SCIENCE states that a human zygote is a: human and b; alive.
Yet again,
alive is not the question. A zygote is undoubtedly alive. Sperm is undoubtedly alive. However a zygote is
not stated by science to be a human. It is classified as a eukaryotic cell. It is recognized as the very beginnings of a developing human, but is not a human yet. The term for it is
preimplantation conceptus. It is not even called an embryo, because at this stage it is unknowable how many embryo will be formed from this zygote.
It is not a human any more than any other cell in your body is a human.
if you can get a scientist or a doctor to show me that a human zygote can turn into anything BUT a human baby unless it dies first, I might rethink my position.
Your position is yours to hold, but it is preposterous and illogical. A human sperm is never going to become anything
but a human baby, so are you going to start calling them humans too?
There have been times in human history where 'human being' wasn't applied until a child was two, or four, or pubescent, or in his/her twenties...
Got any proof for that? I know of practices where children aren't named until their first winter, but that's a different practice entirely. Your parallel to women and slaves is equally flawed, as they are humans who are clearly able to think, speak, etc. A zygote or embryo is not. You are naming inanimate cells as human because you have a fated attachment to them, and your society has impressed upon you that they are human. But as you said, this is a matter of science, not society.
...that magical 21 week old fetus...
Your incredulity to the developmental stage of 21 weeks is almost laughable, especially since the significant developments of the now fetus have been outlined to you.
I find your argument that abortion should be legal because the foster care system is bad to be...
That is not my argument for why abortion should be legal. My argument for that is that I would much rather women receive abortions in a safe, professional environment. The alternative being, of course, coathanger abortions and dangerous drug/alcohol use to induce said abortion. Because as stated, if women want abortions, they
will get them.
The argument of the foster care system is in rebuttal to the counter-point of "there's always the foster system." It's state aside, are you going to adopt? If the answer is no, then you should not suggest it. Otherwise you're just feeding into the problem there.