03/19/2014 08:51 am ET Updated May 19, 2014

Freeing Humanity

On a recent NPR interview about his Oscar-nominated film 12 Years a Slave, screenwriter John Ridley gave his bottom line on the movie. It wasn't the horrors of slavery that he wanted to emphasize. It was a sense of triumph. Slavery is gone. We are now so far from it that we can talk about it openly and dispassionately. "there has to be a sense of pride that we have come this far," he said.

As a psychiatrist, I take a different view. Human aggression was not snuffed out in 1865. Eight decades after the abolition of slavery in the U.S., the Nuremburg trials showed that our collective capacity for cruelty was remarkably resilient.

In his ground-breaking book, The Nazi Doctors, psychoanalyst Robert Jay Lifton chronicled his interviews with the German doctors who experimented on and killed human beings before and during World War II. Lifton's devastating conclusion was that the Nazi doctors were normal people. They were not ghoulish exceptions to human nature. They reflected it. They were everyday individuals drawn in to the cruelty of their time, like most everyone else before and since.

Human aggression did not vanish from the face of earth in 1945, any more than it did in 1865. We have not reined in human nature. All we have managed to do is to peel out of its clutches many of its victims. And there, Ridley was right. We have come a long way. Prejudices related to race, ethnicity, gender, sexual orientation -- all of these are being exposed. And day by day, aggression finds fewer victims.

And now the healthy process of exposing human aggression is moving in a new and perhaps unexpected direction. It is looking beyond our species. A generation ago, the idea of capturing intelligent orcas from the wild and putting them in tanks to entertain children would not have raised an eyebrow. But as the movies Free Willy and Blackfish and the overwhelming response to them have shown, we can see now through an orca's skin, finding the individual inside and wanting to set him free.

It's not just orcas. In 2011, the Institute of Medicine assembled a committee to opine on the fate of our closest biological relatives, chimpanzees. At issue were 436 chimpanzees in U.S. laboratories, where they were injected with HIV or hepatitis viruses, used in behavioral experiments, or forced to serve in other ways. While the committee was instructed to focus on scientific issues, not on ethics, the committee members said loudly and clearly that they could no longer pretend that ethics did not apply to our biological cousins. No, chimpanzees are not human. But what of it? They suffer, and that was what counted.

Americans eat more than one million animals, every hour, according to USDA figures. They also become leather belts and fur coats, stand on their heads at the crack of a whip, are our surrogates in experiments, and are exploited in countless other ways. But they are now becoming recognized for what they are -- undeserving objects of human aggression.

Up until now, many have felt timid about looking too deeply into the suffering of animals, for fear we might seem to be equating slaves or Holocaust victims with other species. But that is not the point. What's at issue is the human tendency toward aggression, and opening our eyes to it is a good thing.

It took centuries to end the obvious obscenity of slavery. It will take far longer to rein in aggression directed at other species. But every step in that direction is healthy and will bring us well deserved pride that we have come this far.