The ongoing capture and slaughter of dolphins at Taiji, Japan—five more mass killings have taken place since the bottlenose hunt last week—troubles us not only because it is cruel but also because of what it says about us as a species.

Since the 1980s, when commercial whaling was finally banned worldwide, we've come to know a great deal more about the minds of marine mammals and many other animals. What we've learned suggests that, like the human animal, many other species, including all whales and dolphins studied to date, are thinking, emotional creatures, and are conscious.

We also know that common bottlenose dolphins (Tursiops truncatus), such as those who were killed or forcefully separated from their families at Taiji, have societies and rules, and some sense of empathy, and right and wrong.

View Images A pod of bottlenose dolphins swim off the coast of Ogasawara Island in Japan Photograph by Hiroya Minakuchi/Minden Pictures/Corbis

How do we know this? One example comes from an article a marine biologist in Scotland published earlier this month in Marine Mammal Science. He describes watching a male dolphin seize a newborn calf from its mother and viciously batter it. The calf died several months later from its injuries.

Humans rarely witness these assaults, but scientists know they are fairly common and that they are part of male dolphins' reproductive urges: They target only the young calves of females they have not mated with. Sometimes, a gang of males will join in the attack. If the calf dies, the female quickly becomes fertile again, giving the males an opportunity to father her next one. In evolutionary biology terms, the males are employing a "reproductive strategy"—one that is found among many species of mammals, from domesticated cats to grizzly bears.

What most affected me about this study, though, was that the biologist also saw several other large male dolphins in the area rush to the mother's aid as she tried to rescue her calf.

They circled the mother and calf and helped the pair to escape. Perhaps those males had mated with her or were her relatives—the two possibilities that evolutionary theory generally offers to explain altruistic acts in animals other than humans.

Animals and Empathy

But there is growing evidence that animals, from mice to elephants, can be empathetic, too, recognizing pain and suffering in others that are not kin.

As the primatologist Frans de Waal has noted, animals that live in complex societies, such as dolphins and chimpanzees, also have "a desire for cooperation and harmony." Perhaps at times this desire even leads to acts of heroism and kindness.

How else to explain the observations of South Korean marine biologists who witnessed about a dozen long-beaked common dolphins (Delphinus capensis) assisting an ailing adult female, whose pectoral fins seemed to be paralyzed?

For more than 30 minutes, the dolphins took turns diving below her to lift her to the surface. As her condition worsened, they tried another tactic: By swimming tightly together, they formed a raft of their bodies so they could carry the female on their backs. Only when she stopped breathing did they begin to disband. Even then, several of the dolphins stayed near her side, touching her body, until it sank from view.

There are numerous other accounts of mother dolphins carrying their sick or dead infants, or of one or two dolphins pushing another to the surface to help it, but this is the first report of a large group of dolphins working together to assist a stricken individual—which is not to say that dolphins rarely behave in this manner. More likely we're not around when they do.

Other examples of animal altruism suggest that at times one species may also help another.

In 2009 biologists saw a humpback whale in the Antarctic save a seal from killer whales as it leaped in desperation through the water. The whale slammed her tail at the orcas, turned on her back, and swept the seal onto the safe haven of her broad belly.

Pilot whales have been seen pummeling and driving away orcas attempting to kill a gray whale calf off the coast of California.

Dolphins have reportedly helped humans by pushing drowning individuals to the surface and chasing away sharks.

And orcas in Norway regularly feed an "invalid" orca that is unable to catch fish, even though he is not a member of their pod.

What are we to make of these accounts? And what do they have to do with what's happening at Taiji?

View Images Dolphins swim in a cove in Taiji, Japan. PHOTOGRAPH BY STAFF/REUTERS/CORBIS

Animal Minds: A Paradigm Shift

For most of the 20th century, scientists taught us to regard other animals essentially as robots.

Nonhuman animals were merely reactive beings: They lacked thoughts and emotions, and we were instructed to disregard any behaviors in other species that we might think of as human—or humane. Only humans loved, laughed, helped others, and grieved.

Scientists also seldom collected data or observations about animals' emotional displays (other than anger) or altruistic behaviors because they were likely to be branded as anthropomorphic sentimentalists.

In the past two decades, however, our understanding of the animal mind has changed. A growing number of scientists, evolutionary biologists in particular, no longer see humans and all other animals as separated by a cognitive chasm.

Rather, they recognize that the brains of all animals, including the human animal, share many of the same qualities and abilities because they are designed for many of the same tasks and have a general, common ancestry.

That's why scientists are now searching for the roots of empathy and altruism in other species and are collecting the kinds of anecdotes I describe here. (Thirty or more years ago, these meaningful observations would likely have ended up in the dustbin.)

Animals do think and feel, and sometimes they surprise us by acting humanely. Given a chance, the humpback will save the seal.

The Dolphin Killers

And then there is Taiji. The human fishers who are working there—forcibly corralling dolphins, holding them in pens for days in close quarters, tearing calves away from their mothers, and killing many—confound us because their actions are so utterly inhumane.

And unnecessary. Very few Japanese dine on dolphin meat; no one needs it to survive.

Killing wild dolphins may be a tradition there, as the country's government insists, but traditions are not inviolable. They change when they no longer fit a society's needs or are recognized as immoral.

"That tradition was made only when the world, and Japanese Fishermen did not know what it meant to do harm to the Dolphins," Yoko Ono Lennon wrote in an open letter to the Taiji dolphin hunters and Shinzo Abe, Japan's prime minister, on January 20.

But the world, the fishers, and the Japanese government all know now what the killing at Taiji means.

Who Is a Person?

Many of us are struggling these days to redefine our relationship with other animals. There are calls for certain species, including whales, dolphins, elephants, and chimpanzees, to be considered persons with rights.

It required many centuries for human societies to recognize that other people had rights, and extending some kinds of rights—at a minimum, not being kept in captivity or used in biomedical research—to other animals is an even greater challenge. It might even seem quixotic, but a growing list of countries, including Japan, no longer allow invasive research on chimpanzees.

And that we are wrestling with this issue at all suggests that we know that our treatment of other animals is not always right, and that events such as those at Taiji are wrong.

What Taiji Shows

What, then, does Taiji reveal about our human nature?

That in spite of what we have learned, we can persist in being knowingly and brutally cruel—as inhumane and unfeeling as we once regarded all other animals to be.

But take another look at Taiji's shores. Besides the fishers, there are other people, including Japanese citizens, who have gathered to bear witness, to document the horror, and protest the killings.

There is no way for the dolphins to know of these people's actions. But they are there, working on the dolphins' (an unrelated species!) behalf, because it is the right thing and the kind thing—the humane thing—to do.