Again, nobody has ever disagreed on the basic biological steps.
The debate is about at what point your "life" beings, as in your life as an independent being, not something that is a just a part of another thing.
Independence is irrelevant. If the embryo was just a part of another thing like the say, the mother, it wouldn't be so clearly different biologically.
In this case, I am using independent to mean separate. Even if you are an adult that depends on others to survive, you are still independent in the sense that you are a separate being, not part of anyone else.
Again, it's irrelevant. If something happened during my development inside the womb, it wouldn't matter that you call me a separate individual after birth. That development is part of my life. It can have very profound impacts on my life and none on that of my mother.
An embryo or non viable fetus has a very different kind of dependence on the mother. It simply can't exist separately from that specific woman.
IVF embryos exist outside of mothers. They are grown for days without the environment of a specific woman, and they can even be transplanted into new women. And even if they couldn't, so what? That's the evolutionary path our species has taken. Every human in existence started out in the same fashion, that's part of the biological development for our species. Other species lay eggs, but the embryo is still a new individual.
When is having 46 chromosomes the definition of being human?
It's one defining characteristic. There's no human on earth alive with only 23 chromosomes. You going back to sperm and egg is too far to consider my life beginning. Even more to the point, my life began with a specific sperm and egg.
Let's go over some basic facts. The genetic assortment that occurs after fertilization makes a new genome. The cells begin dividing, and forming layers that will later develop into specific tissues. The cells are metabolically active, with many important biochemical pathways. The pathways in the embryo are different from those of the mother, they need to be for development to continue in that environment. If those biochemical pathways are interrupted, the cells can die. It has unique biological rhythms which can be measured.
It's living tissue (required for a human), it's a new genetic assortment (required to differentiate from the mother), it has unique biological rhythms to that of the mother (also required for a different individual), it has it's own organs (a requirement) and it can be killed (ending the life of the new human). Clearly that's a new individual.
The really odd thing, is that none of this matters. I'm still pro-choice, because I don't believe that I should be able to tell someone else what to do with their life and body. I think I should be able to end my life if I want. I think IVF is great for couples who can't get pregnant in the conventional fashion, even if it means embryos will be destroyed, or used for research. And the fact that I think life begins when there is clearly living tissue and a new genetic assortment has sweet Ƒuck all to do with what I think about abortion. My views are closer to Colpy's perhaps, which as you and others have already mentioned, is pretty much on par with what the various provincial Colleges of Physicians and Surgeons already have in their codes of practice.
