As evolutionary biologists and cognitive neuroscientists peer ever deeper into the brain, they are discovering more genes, brain structures and other physical correlates to feelings like empathy, disgust and joy. That is, they are discovering physical bases for the feelings from which moral sense emerges—not just in people but in other animals as well.

The result is perhaps the strongest challenge yet to the worldview summed up by Rene Descartes, the 17th century philosopher who divided the creatures of the world between humanity and everything else. As biologists turn up evidence that animals can exhibit emotions and patterns of cognition once thought of as strictly human, Descartes’s dictum, “I think, therefore I am”, loses its force.

For many scientists, the evidence that moral reasoning is a result of physical traits that evolve along with everything else is just more evidence against the existence of the soul, or of a God to imbue humans with souls. For many believers the findings show the error of viewing the world in strictly material terms. And they provide for theologians a growing impetus to reconcile the existence of the soul with the growing evidence that humans are not, physically or even mentally, in a class by themselves.

The idea that human minds are the product of evolution is “unassailable fact”, the journal Nature said this month in an editorial on new findings on the physical basis of moral thought. A headline on the editorial drove the point home: “With all deference to the sensibilities of religious people, the idea that man was created in the image of God can surely be put aside.”

... contd.