analog

You realize, of course, that there's no reason to INclude either fetus, or embryo, in the definition of "human being"- nor is it currently included in any such definitions.

Not to mention that "human being" is a meaningless term- it just means "a human". "Human" doesn't indicate life, sentient capabilities, brain or brain activity, spine, hypothalamus, nervous system, etc., etc. The body of a dead human is just as much a "human" as a live body. Pointing to a corpse, you would similarly indicate it as being a human being as you would an embryo in early development. Therefore, saying that an embryo is "human" and insisting that means it's alive, sentient, or has any brain activity, is both foolish and incorrect.

Human is just the form. What's important is the life, and that's where people argue the point... just where it begins. Some would say that conception- the simple act of fertilizing an egg- is the beginning of life. They're basically saying that, from the onset, that tiny little bundle of replicating and dividing cells is a person. Scientifically, that's a ludicrous notion- just like when a person is declared clinically brain dead, they cease to be a live person. Machines can maintain the biological processes of the body, such as respiration and circulation, so that the body can be harvested for organs- but the person is dead. An embryo without a brain, or brain activity, is no more a "living person" than a body with clinical brain death.

I think most everyone agrees on a time during the pregnancy where there should be a cut-off, because it is a living creature capable and most plausibly engaged in brain activity which indicates true "life". For most, that's the point at which the brain is developed enough that the brain activities indicative of human sentient life are present. Prior to that, it's just a sac of cells and fluids, not a life.