You have to wonder whether the people who believe that animals should have equal standing with humans ever consider the lessons to the contrary presented to us every day in the tabloids and women's magazines. In some ways I find these evidences of human complexity more convincing than the standard secular arguments that we humans are qualitatively different from (okay, I'll go for it!) lower forms of life.
Attempts to convince skeptics of the chasm between man and the rest of the animal world generally take one of several routes. There is the argument from Blessed Mother Teresa: Human beings living at the pinnacle of altruistic love and self-forgetfulness have no match in other species. Sure, animals will die for their young, and domesticated animals may risk their lives for their human families. But humans at their best ratchet heroic selflessness to a much higher degree. They can love other people sacrificially even in the absence of familial, tribal, national or even religious ties. As Blessed Mother Teresa used to put it they can love even "Christ in distressing disguise,": the diseased, addicted, abused, old and unlovely — yes, and the selfish and nasty. This is a height that relatively few humans attain, but no animals that I know of approach. A dog may be loyal to an abusive owner, but hardly to an abusive stranger.
The existence of such people constitutes a compelling argument — perhaps the most compelling argument — for the special status of humanity, but true-blue PETA types seem to believe that dolphins have it in them to equal Blessed Mother Teresa.
So there is the argument from Einstein — meaning not just that we are more intelligent than other species, but that we are uniquely (among earth's creatures) capable of self-awareness, as well as the ability to plan, design, discern long-term cause and effect, perceive mental relationships, draw analogies, develop systems, and even construct arguments for and against Intelligent Design.
This too seems to me a compelling argument. After all, ants create complicated societies, but always the same kind of complicated society. There is no animal equivalent of Montaigne, Locke, Robespierre, Marx or Mao to revolutionize ant colonies, wolf packs, whale pods, or elephant herds.
Still, advocates for the animal kingdom can argue that intelligence is not the basis for value or rights — an argument that we ourselves make on behalf of the unborn and the disabled. And they can theorize (daringly) that other life forms are on a long evolutionary trek toward greater self-awareness and volition, claiming equal rights for them on the basis of this far-off, spectacularly unlikely possibility.
But there is another non-theological argument for the essential distinctiveness of human beings, one that strikes me as unanswerable, and that is the argument from the tabloids, meaning the argument from human psychological dysfunction.
Now, it's true that brain damage can provoke bizarre behaviors in any species equipped with a brain. And it's true that animals (especially domesticated ones) can also suffer from emotional and behavioral dysfunctions (hence the emergence of pet psychologists, who address the unhealthy habits of mistreated, over-indulged, phobic or stressed animals). Take the pampered pet dog who eats itself into an unhealthy state.
But do these obese dogs come to view themselves with disgust or self-loathing, resolve on a diet program, and organize a support group? Do we see them dieting and then rebounding, dieting and then rebounding? Finally, do we find some dogs who move on to the more serious pathology of bulimia or anorexia, or obsessive exercising? Where are the Mary-Kate Olsens, Lindsay Lohans or Nicole Simpsons of the animal world?
Domestic animals exposed to an oversupply of food and an undersupply of healthy activity simply pig out (so to speak) and die early, without demonstrating the kind of struggling toward health and normalcy that most human beings experience at one time or another in regard to our own personal weakness.
Am I suggesting that the diet and exerciser infomercials offer evidence that humans rank at the top of the material world's hierarchy? More modestly, let's just say that they show which species has the greatest need for divine redemption.