2. any living or extinct member of the family Hominidae characterized by superior intelligence, articulate speech, and erect carriage
This definition has serious problems, at best.
The two parts of this, taken equally, implies that a human being must be (ignoring the mention of extinct) both living and have articulate speech and erect carriage. If not, no human being. This would mean that those born seemingly without the ability to communicate, or those who cannot walk are not human. Infants possess none of these abilities. I think, rather, that this definition is unfortunately too ambiguous to be useful.
While I can appreciate that the newly conceived doesn't look anything at all like an adult, or act like an adult, does not communicate like an adult or consume the food an adult does, and that there are many compelling emotional and practical reasons for finding a way for it to not be human, there just isn't any
science to support it. Does an embryo look like a 3 month, 1 day old fetus, for those that think abortion is wrong after the 3rd month, does a 3 month old fetus look like a 9 month old fetus, does a 9 month old fetus (still attached to the mother in a "paracitic" way) look like a 2 year old, like an adult, etc. Do any of them act like the other? Do any of them eat the same food or in the same manner? Do all of them display the same level of cognizance?
Regarding the comment about paracitic, until we developed formula, infants were still parasitic. Did they suddenly gain the right to be protected once they were freed from being attached to their mother?
There are many types of developmental processes which that we undergo until death. We are not done cooking, even at birth. The brain is still growing until, some researchers say, until somewhere between 11 and 15 years old. We don't stop growing in height until 22 or 23. We don't start having the ability to communicate until sometime in utero. When we become aged, our bodies start degenerating - backwards development, in a sense. The process is continuous.
If the newly conceived isn't
yet human, what makes it human and when does that happen? The definition above will not work unless you deny human status to many groups.
And you can't say that the newly conceived is
less human. If so, based on what? Based on the definition above? If so, people that are handicapped are less human
than people that are not. If you were once fully human but then were in a crippling accident, do you become less human?
I am not arguing that their abilities to function
as humans is not diminished. It is
right and good for us to try to prevent what makes people handicapped or crippled because it would allow them to act in a way that fully actualizes their potential as human beings.
Not to mention we would have to have a scale on which we
grade being human.