Why are we good and evil? A single quality may be at the root of it

The human capacity for both good and evil has long mystified philosophers. Evolutionary biology suggests they are both offshoots of one of our oddest character traits

By Graham Lawton

“THE evil that men do lives after them; the good is oft interred with their bones. So it will be with Dzhokhar Tsarnaev.” So said Judge George O’Toole before sentencing Tsarnaev to death for his part in the 2013 Boston Marathon bombing. During the trial, it emerged that the killer was well liked by his teachers and friends, had been compassionate to people with disabilities and had apologised to victims and their families. But, said O’Toole, his goodness would always be overshadowed by his hateful act.

The human capacity for both good and evil, often within the same person, has long been recognised and puzzled over; O’Toole was quoting the Roman general Mark Antony in Shakespeare’s Julius Caesar. What is it about us that endows us with such diametrically opposite propensities?

Evolutionary biology has an answer, and it doesn’t reflect well on human nature. Acts of both good and evil are driven by altruism – and that is ultimately selfishness in disguise.

For a long time, altruism was a biological mystery. The prime directive of evolution is to pass on our genes to the next generation. Engaging in costly behaviours with no obvious survival pay-off seems to go against that grain. The polymath J. B. S. Haldane eventually twigged it: individuals mostly make sacrifices for close relatives, and hence help to usher copies of their own genes into the next generation. As Haldane put it: “I would lay down my life for two brothers or eight cousins.” Acts of true selflessness exist, but these are …