Working out the moral implications makes a perfect puzzle for a large-brained, highly social species like our own. The existence of a brain in animals does not alter the case for animal rights, any more than does the existence of legs. Chickens have two legs and walk upright. They seem to be leaning toward apes, dogs, dolphins, etc. Our Declaration of Independence says that our rights come from our Creator.
Animal rights require a source, just as human rights do.
Our Constitution extends this notion. Based on the belief in human rights from a Creator, the Constitution develops the idea that government does not dispense rights, but has only the rights delegated to it by people who previously possessed them. In fact, if evolution is true, then there is no source of human rights. If men are merely the product of random, purposeless processes, their lives can have no more purpose than the events which created them. Nor can there be an objective standard of morality.