Interesting question - the obvious answer is that the child is more human because they are literally human, I assume your expecting a more philosophical answer but I don't really have anything, its pretty simple humans are Homo sapiens, dogs are Canis lupus familiaris, and Felis catus are domestic cats. Everything identifies as its own category.

Of course this is before you incorporate therianthropy, transids and other people who don't ID as human. Everything changes when you start talking spirituality and all of the above are valid in their identity, I just didn't know how to include it in my answer.