This is the Great Problem with the abortion issue: when does an egg/sperm combo become a "human being? Science can't tell us because it's based on empirical evidence and repeatable results. But no zygote, embryo, or fetus can tell us anything. But religion 'can' because it's based solely on faith, what some "holy book" and/or religious leaders decide is true. And they can't even agree which is evidence that they don't know jack crap more than anyone else.
That a 'soul' exists is not based on any empirical evidence. There is nothing to test or observe. It's 100% a matter of belief. Some think our laws should be based on these religious beliefs even though they are not based on anything but belief and others may/do not agree with those beliefs. That is the ultimate conceit. This is what I believe; therefore you must live by my beliefs rather than your own. After all, I'm right!
My personal opinion is that a fetus is not a baby until it has a fully functioning brain and is viable. Until then, it is just in the process of becoming a baby just as a seed eventually become a flower. But the difference between me and the so called pro-life people is that I recognize that is MY belief and not necessarily THEIRS. But, unlike them, I would never tell a woman that she HAS to have an abortion. But, damn, they sure feel they have the right to tell others to live by their beliefs.