Most of us wouldn’t balk at the opportunity to help the people closest to us, such as our parents and siblings. And it’s not hard to see that urge from an evolutionary standpoint: Natural selection might favor people who help relatives, increasing the odds of their family genes passing on to the next generation. But what about more distant relatives whom we barely know? What would compel us to help them out in their times of need?

In a recent study, published in the journal PLOS ONE, anthropologists from the University of Utah have introduced a new theory on kin selection based on moral regulation of behavior and how it’s impacted by social norms. Their findings show that our propensity for helping family members, including distant ones, may have less to do with liking them and more to do with our duty, responsibility, and reputation.

"We are a very special species because of how good we are at making social rules and enforcing them," said Doug Jones, author of the study and an associate professor of anthropology, in a statement. "This means relations among kin work differently in humans than in other species.”

Jones and his colleagues sought to expand on the classic kin-selection theory using their unique concept of socially enforced nepotism, which encourages us to help distant relatives. The classic kin theory is based on Hamilton’s rule, a biological formula stating that any organism can get more of its genes into the next generation by sacrificing its own well-being for kin. However, this theory only holds true for closer relatives.

Jones said that the classic theory of kin selection holds that "you shouldn't be terribly nice to distant kin because there isn't much genetic payoff. Yet what anthropologists have observed over and over is that a lot of people are pretty altruistic toward distant kin." His research aimed to beat Hamilton’s rule using his team’s new mathematical simulations of small-scale societies with tens to hundreds of people. Their models show that this is possible when distant kin help each other to build their own reputations.

"That may sound circular, but it works," Jones explained. "When you work through the math, it turns out that natural selection can favor a scheme where you help some members of your kin group — who will never pay you back — because it boosts your reputation and leads other group members to help you."

In their computer simulations, the research team asked people to follow one of two mathematical rules which reflect social norms that dictate how much a person helps other people and receives help in return. They were "almost-balanced reciprocity, where you help other people only as much as they help you,” and "generalized reciprocity, where you might be very helpful even to someone with no ability to pay you back because other people see this, they like what they see, it boosts your reputation, and they reward you for it."

The results of the simulation revealed that people who follow generalized reciprocity gain an evolutionary advantage. People who help distant relatives without expecting help in return tend to have more offspring compared to people who expect something back. Jones said this may explain why “small-scale, kin-based societies share food and other goods because they're supposed to, without expecting an exact return from the recipients."

“It still matters that people are kin,” Jones added. “It doesn't work with just a random group of individuals. And though the math doesn't work for really large groups the size of nations, the simulation might still be relevant insofar as we think of other people as our distant kin. The emotions that evolved in small-scale societies might still influence how people treat distant kin, or those they think of as distant kin, in modern societies. That's speculative but a possibility."

So helping random people may no longer further the spread of our genes, but those random acts of kindness still boost our psychological well-being, something that’s been shown in other research.

Psychologists from the University of the South in Tennessee, for example, divided 500 participants into four groups: the first completed acts of kindness to improve the world (picking up litter); the second completed acts of kindness for other people (buying a friend a cup of coffee); the third performed acts of kindness for themselves (exercising); and the fourth was a control that did nothing. Participants who performed acts of kindness for the world or others reported a boost in mood and positive emotions that was triggered by the release of dopamine, a neurotransmitter responsible for reward and pleasure centers in the brain.

Source: Jones D, et al. Socially Enforced Nepotism: How Norms and Reputation Can Amplify Kin Altruism. PLOS ONE. 2016.