Survival of the nicest

In this brief lull between taking down ghoulish Halloween decorations and putting up cheery Christmas lights, let’s take a moment to wonder — why?

Why give candy to each child who knocks? Why buy presents for friends and family, including every last third cousin twice removed?

The answer, at least in part, is generosity. Humans are social animals and our society works best if we cooperate, helping each other out as needed.

But this generosity seems to contradict Darwin’s theory of evolution through natural selection. Evolution is the change in inherited traits within a population over time. Natural selection is when individuals with useful traits are able to live longer and have more babies, passing on those traits.

So, evolution seems like it should reward selfishness. You need to beat out the competition for your traits to survive over time, right? Yet, generosity and co-operation exist throughout the natural world.

Impalas take turns grooming each other. Birds call out to show others a new food source. Elephants form defensive circles to protect the young and weak. Deer flag their white tails and squirrels squeak an alarm if they spot a predator. All these behaviours cost the individual, but benefit the group.

So, co-operation must be evolutionarily stable. But how does it work in humans? To understand, we must look into the brain.

Dr. Jordan Grafman, a National Institutes of Health neurologist, wanted to see what is happening in people’s brains when they give to charity. In a 2006 study, scientists in Grafman’s lab gave participants money and asked them either to donate it or keep it for themselves.

The scientists then used a technique called fMRI (functional Magnetic Resonance Imaging) to look at changes in brain blood flow during these decisions.

It turns out that both decisions activate the brain’s reward system (the mesolimbic pathway). The feel-good chemical dopamine is released when participants keep and donate money.

However, only donation activates the brain’s social region (the subgenual area), associated with the bonding and empathy hormone oxytocin. Generosity is chemically tied to feelings of social belonging.

Basically, our brains chemically prioritize group over self — an evolutionarily sound tactic, since humans are safer and smarter as a collective than as individuals.

Another way scientists explain the evolution of human cooperation is through mathematical models and game theory. The most famous example is the Iterated Prisoner’s Dilemma, in which each player decides to cooperate or cheat his partner.

In a single game, cheating gives you the highest reward, but mutual co-operation is best over multiple games. In a 2013 study of the Dilemma, University of Pennsylvania scientists Alexander Stewart and Joshua Plotkin found that strategies of generosity (in which players co-operate and forgive each other) were the only successful strategies in a large, evolving population over time.

So really, buying all those Halloween candies and Christmas gifts is not foolish extravagance at all. We are just following the path of human evolution, where not just the fittest survive, but also the nicest.

Kate Henbest is a grad student in the Laurentian University/Science North Science Communication program. Have a burning science question? Send it to [email protected].