Animal Rights: Liberty and Justice for All

Rights are the protection of interests. The most fundamental right is the prohibition against coercive exploitation: not to be treated as property, not to be caused pain and suffering. Who ought this basic right apply to? All and only humans? That does not really specify what it is that qualifies them. Being really smart? Being capable of language? These criteria would rule out a number of humans, and why are these criteria relevant to who is eligible for basic rights? All and only sentient...