You're confusing the social conventions with the general philosophical arguments
I do agree with thag on this point. Social trends don't always represent the reality that underlies society.
Its like there are different levels of the world, or of life. There is life, and then there is society and the social norms that are superimposed over it.
Social norms are always changing too.
Concerning the other points Thag makes, I understand where you are coming from when you are saying that the baby has no awareness of itself, but more often than not, you are failing to realize that philosophy and worldview are inherent in one's perceptions and perspectives.
As much as you might sway away from the things that make us all human, limitations and the like, you are never really outside of it. Your love of science is preceded by an inherent philosophy that gives you such a worldview with the value of science.
So as much as you might not consider them humans yet, you cannot escape the reality that this all depends on what being human means to you in the first place, a philosophical inquiry.
You might look at your body as limited, your emotions as irrational, and take yourself(and everybody else) to be nothing more than a self aware minds, and this is valid logic when it pertains to the underlying philosophy and worldview that you operate from.
One can even say that logic is only of value when viewed from a logical perspective, to Logic.
And what you and others fail to realize is that going back and forth on trying to prove whose logic is valid and whose isn't will do nothing in the end because it is the difference in worldviews that dictates things, meaning relative to one worldview, the logic that comes with it is valid, as with the other.
We should start making it a point to try and 'step' out of our worldviews, realize that what we place an emphasis on in our lives is very much predicated on underlying conditions. Perhaps we can then become truly Self-Aware, in its realest form.