Science cannot answer metaphysical questions, just as religion cannot answer questions proper to science (religion can, however, utilize scientific facts to clarify it's beliefs about various things. All truth is God's truth and scientific and religious truths cannot contradict each other).
While the time of ensoulment has been debated for centuries (my Church teaches it occurs at conception), even if we are reduced to admitting we don't know, it is always better to err in favor of it being a human being. In the specific case that we are discussing, if you have good reason to believe something is a human life, but are not sure, it’s better to treat it as if were a human life.
If one sees a bag lying in the road that is such a size and shape that it could be either a baby inside or a bunch of old clothes, it’s better not to run over it than to run over it.
I understand and pretty much agree with you; but we live in a country where laws and regulations are not really guided by any specific religious belief or specific moral system. They’re the product of a consensus morality and science.
Maybe someday we’ll get where you want us to be. (I’m personally hoping that science someday moves toward encompassing metaphysical issues. I don’t expect to see it in my lifetime.)