During pursuit of a dastardly fiend, Sherlock Holmes remarks upon the "curious incident of the dog in the night-time." A baffled inspector asks exactly what it was that the dog did to provoke such fascination. Nothing, Holmes replies, it was the fact that the dog did nothing that was curious. The same might be said about scientific discourse. Just as he pondered why the dog did not bark when the crime was committed, Holmes might wonder why today's scientists are mute on the subject of ethics when discussing mental commonality between ourselves and other animals.
Primatologist Frans de Waal insists, in a recent article in Nature, that theory and data overwhelmingly establish human-animal continuity of mind. Quintessentially human attributes such as "culture, imitation, planning and the ability to adopt another's point of view" are found across species, including even the taxonomically-made-low octopus. Diverse scientific discoveries -- from evolutionary theory and neuroimaging to experiments on mirror self-recognition, facial recognition, empathy, and reconciliation -- confirm relatedness from genes to brains.
Other animals suffer psychological trauma comparable to humans when similarly subjected to incarceration and torture and the line distinguishing a human self from that of a cousin ape blurs when nurture fails to follow patterns that nature anticipates. When reared by humans, chimpanzees develop a mixed primate identity.
Even inference, the logic chain used to weave discrete findings into a coherent storyline, finds symmetry. What we learn about human minds can be applied to animals with rigor equal to what we learn in reverse. Consequently, attempts "to single out distinctly human capacities", de Waal maintains, "have rarely held up to scientific scrutiny." From Darwin onward, a growing consensus has it that there is "no fundamental difference between man and the higher mammals in their mental faculties."
And yet, scientists making the case for mental continuity are often singularly silent and discontinuous when it comes to ethics. To gain their insights, these researchers do things to other animals that are prohibited for humans who share comparable mental capacities. Making distinctions at the level of skin (or fur and feathers) is discomfitingly reminiscent of other times when scientists have played a less-than-savory role in social policies. Continuity among species extends to continuity between thought and action and science and ethics. It's elementary, my dear Watson.
G.A. Bradshaw is director of the Kerulos Center and author of "Elephants on the Edge: What Animals Teach Us About Humanity," new from Yale University Press.