What hard facts do you have to say that a fetus isn't a living human being? To say that it's not a human being because it hasn't reached an arbitrary threshold of development is a moral argument, not a scientific one. Life begins at conception. Stages of development don't determine whether or not something belongs to a particular species.
You could also under this definition call an amputated leg a living human being.
Um...no? Find me an amputated human leg that continues to develop, gains new functions, and grows with time...
Continuing to develop, gain new functions and grow over time is not an accurate definition of a living human being. Some living human beings are 60 years old, and will no longer gain new functions or grow over time / develop. If you hook the amputated human leg up to something that will pump blood the correct type of oxygenated blood in and out of it, it will stay alive, at least, for a while. So it's living, has skin cells that will divide (create new cells) over time, and isn't required to gain new functions or grow or develop.
Anyways, my point with this whole leg that was that "it's the same species therefore it's a human" was a bad argument.