The internet is full of scientific explanations, Finn - knock yourself out.
Here is a small excerpt:
Thibodeau, G.A., and Anthony, C.P., Structure and Function of the Body, 8th edition, St. Louis: Times Mirror/Mosby College Publishers, St. Louis, 1988. pages 409-419
"The science of the development of the individual before birth is called embryology. It is the story of miracles, describing the means by which a single microscopic cell is transformed into a complex human being. Genetically the zygote is complete. It represents a new single celled individual."
Finn, I think what you're mistaking here is the fact that from conception to
birth there is the process of human cell formation (zygote) to the embryonic development up to the time when birth that takes place and a human being is born. Human life begins at birth, conception initiates the process towards it.
What you've cited doesn't speak, at all, to when human life begins.
I understand that your opinion is that a fetus is not a human being until it is born and takes its first breath of air. I can find evidence of very many opinions that hold that human life begins with fertilization of the egg by the sperm, but I can find nothing that supports the idea that either of these opinions is a fact.
The Supreme Court in Planned Parenthood v Casey
held that states could restrict or or ban entirely abortion (except in the case of the life or health of the mother) based on the point of fetus viability - 22 or 23 weeks of gestation.
While this isn't specifically a decision as to when a fetus can be said to be a human life, you offered as proof of the fact that a human life doesn't begin until delivery that abortions are legal. Since an abortion can, constitutionally, be considered illegal well before the fetus takes it's first breath, the support you'e offered for considering your opinion a fact, falls apart.
With some restrictions, abortions are legal and it's unlikely that this will change in the forseeable future. In general the public prefers a sort of midway approach which allows abortion up until a point in the development of the fetus. That point is not birth.
The point at which human life begins is an opinion or a belief; not a fact.
I appreciate that it might make Pro-choice advocates more comfortable with their position if science told us the fetus is not a human being until it is born, but you just don't get that comfort.
This is not to judge you or anyone else for your position. You believe what you believe and so do I. The law has decided the issue for now and unlike Rex, I see no reason to challenge the good faith of either Pro-choice or Pro-life beliefs.