Did you read the comment I posted with the article?
Ultimately, there is no specific beginning and ending of human life. A human corpse is not alive, but there is no meaningful instant that separates alive from dead.
Biology is almost entirely about continua, and human biology is no exception. Conception is a continuous process which ultimately has no meaningful specific dividing time for any property, including rights.
It is not that we aren't able to say scientifically when the beginning is; it is that scientifically, there is no beginning. Science recognizes the fact of continua in almost all physical observables. This is so fundamental to science that it is usually presumed to be understood, despite language about specific dividing times.
If a corpse is not alive, then when did it's life end?
If you're asking strictly secular sources, that would probably be your conclusion. However, those two moments by which you are baffled are clear and simple to Him who gives life.
Hoping for the answers to life and death and existence from science alone is like hoping for a typewriter to sing an aria.