Saletan considers animal rights and the "myth of animal equality":

Opening your mind to science-based animal rights doesn't eliminate inequality. It just makes the inequality more scientific. A rat can't match a pig, much less a boy.

And it's a continuum, right? Hence Spain's new law defending ape rights:

GAP is scientifically honest. And science doesn't show mental parity between great apes and human adults. What it shows, as the group's president acknowledges, is that great apes "experience an emotional and intellectual conscience similar to that of human children." Accordingly, the Spanish proposal doesn't treat apes like you or me. It treats them like "humans of limited capacity, such as children or those who are mentally incompetent and are afforded guardians or caretakers to represent their interests."

I understand the intuition that humans are different in kind than animals. But science won't allow such absolute categories.