Nav: Home

Why people help distant kin

June 15, 2016

SALT LAKE CITY, June 15, 2016 - It's easy to understand why natural selection favors people who help close kin at their own expense: It can increase the odds the family's genes are passed to future generations. But why assist distant relatives? Mathematical simulations by a University of Utah anthropologist suggest "socially enforced nepotism" encourages helping far-flung kin.

The classic theory of kin selection holds that "you shouldn't be terribly nice to distant kin because there isn't much genetic payoff," says Doug Jones, an associate professor of anthropology and author of the new study. "Yet what anthropologists have observed over and over is that a lot of people are pretty altruistic toward distant kin."

Jones seeks to expand the classic theory with his concept of socially enforced nepotism, which he calls a "souped-up version of the theory of kin selection" in his study published June 15, 2016, by the Public Library of Science's online journal PLOS ONE.

Socially enforced nepotism "depends on the moral regulation of behavior according to socially transmitted norms," he writes in the study.

The findings suggest that "a lot of why you help your kin, including distant kin, isn't necessarily because you like them so much but because it's your duty, your responsibility, and other people care whether you do it," he says.

Basic kin-selection theory lacks social norms, so "you as an individual decide on your own how much to help somebody just because of how much you like them or don't like them," Jones says. "But with socially enforced nepotism, you help somebody even more because of the social pressures to do it and social rewards for helping. It improves your reputation, and improved reputation gets you more help from other people."

He says socially enforced nepotism "may help explain the phenomenon of generalized reciprocity, where members of small-scale, kin-based societies share food and other goods because they're supposed to, without expecting an exact return from the recipients."

This expanded theory of kin selection reflects the fact that "we are a very special species because of how good we are at making social rules and enforcing them," he adds. "This means relations among kin work differently in humans than in other species."

Jones performed desktop computer simulations of small-scale societies with tens to hundreds of people. What about large and developed nations?

He says that in his theory, "it still matters that people are kin. 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," Jones says. "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."

Simulating a small-scale society

Classic kin-selection theory is based on a famous biological formula named Hamilton's rule, which deals with how altruism evolved among kin. It holds that an organism can get more of its genes into the next generation by sacrificing some of its own well-being to increase a relative's fitness - but that holds true for closer kin and not for distant kin. In other words, "you should help people in proportion to the fraction of your genes they share," Jones says.

His new mathematical model or simulation shows it is possible to beat Hamilton's rule if distant kin help each other according to their reputations. Each player's reputation depends on how much they help other people, and on the reputations of those they help.

"That may sound circular, but it works," Jones says. "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."

Jones' new study grew from his earlier work involving what he calls the Brothers Karamazov Game, loosely based on the novel.

"Two brothers have a chance to help a third brother," he says. "If the two decide independently of one another whether to help, Hamilton's rule applies. But if one approaches the other with an offer, 'I'll give extra help if you do too,' then the level of altruism toward kin may be higher than the simple version of Hamilton's rule predicts."

Compared with that simple, three-person game, the new study "presents a more complicated case involving a game with lots of players of varying ability," Jones says. "Players reward one another according to their reputations, where your reputation is a function of how much you help other players, and of their reputations."

Playing a game of norms

The study used computer simulations "to see if we can come up with a model to help us understand what we see out there in the real world," Jones says.

The simulations use game theory - which "has a bunch of people who choose different strategies and get payoffs depending on what strategies they choose and what strategies other people choose" - and population genetics, in which "the payoffs are more offspring, and you ask how does the population evolve, how does gene frequency change?"

People in the simulation followed one of two mathematical rules, which Jones says reflect social norms dictating how much a person helps others and vice versa:

-- "Almost-balanced reciprocity, where you help other people only a much as they help you."

-- "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."

"Both rules are floating around and you see how they compete with each other in a simulation," Jones says. "Some people follow almost-balanced reciprocity, some people follow generalized reciprocity and some compromise. Some players are really strong and can easily help other people, and others are weak and cannot."

The simulations translated into numbers the extent to which someone helps someone else, and how much that boosts their reputation.

"The math is similar to coming up with Google ranks," Jones says. "Google assigns every web page a certain score. Everyone's score depends on the score of everyone who links to them."

Help others, help yourself

After running the simulation "for a wide range of values," Jones found that people who engage in generalized reciprocity "win the evolutionary game. People who help distant kin even when those distant kin can't help them back have more offspring than those who insist on repayment."

The simulations also showed that if people stuck strictly to their norms -- either always expecting or not expecting something in return for help -- then whichever norm was most frequent at the start of a simulation won the game. But when the simulations also included compromise norms -- helping others while expecting repayment only some of the time -- then generalized reciprocity predominated.

"If you're helping distant relatives and they're not paying you back, then all the balanced reciprocity guys [those expecting return payment for help] are looking at you and saying, 'What a loser,'" Jones says. But if you help others and expect something in return part of the time and not at other times, "then you do better evolutionarily."

Jones' study notes: "Some anthropologists argue that human kinship, insofar as it is socially enforced, is divorced from biology. The argument here, on the contrary, is that kinship is uniquely elaborate and important in our species because norms that push people to treat distant kin like close kin have been favored by natural selection."
University of Utah Communications

75 Fort Douglas Boulevard, Salt Lake City, UT 84113
801-581-6773 fax: 801-585-3350

University of Utah

Related Natural Selection Articles:

Ongoing natural selection against damaging genetic mutations in humans
Investigators report that, as a species, humans are able to keep the accumulation of damaging mutations in check because each additional mutation that's added to a genome causes larger, and larger consequences, decreasing an individual's ability to pass on genetic material.
HIV co-infection influences natural selection on M. tuberculosis
While M. tuberculosis has been evolving with humans for thousands of years, HIV co-infections create host immunological environments that this bacterium has not encountered before and could, therefore, be nudging it to evolve new characteristics.
The selection of archaeological research material should be re-evaluated
A systematically collected material produces a more exact image of the excavated objects.
Climate change altered the natural selection -- large forehead patch no longer a winner
In a new study, researchers at Uppsala University have found evidence of that climate change upends selection of face characteristics in the collared flycatcher.
How natural selection acted on 1 penguin species over the past quarter century
University of Washington biologist Dee Boersma and her colleagues combed through 28 years' worth of data on Magellanic penguins to search for signs that natural selection -- one of the main drivers of evolution -- may be acting on certain penguin traits.
More is better when it comes to online product selection
Retailers should take advantage of the unlimited retail space online and offer everything they sell.
Selection pressures push plants over adaption cliff
New simulations by researchers at the University of Warwick and UCL's Institute of Archaeology of plant evolution over the last 3000 years have revealed an unexpected limit to how far useful crops can be pushed to adapt before they suffer population collapse.
Long-term response to selection predictable regardless of genetic architecture
In their latest publication in the Proceedings of the National Academy of Sciences (PNAS) Tiago Paixao, Postdoc, and Nick Barton, Professor at the Institute of Science and Technology Austria, addressed the controversial role of gene interactions (or epistasis), where the effect of one gene is affected by the presence of other genes, in the response to selection for two extremely different scenarios of evolutionary mechanisms.
Applying parameter selection and verification techniques to an HIV model
Physical and biological models often have hundreds of inputs, many of which may have a negligible effect on a model's response.
Evolutionary 'selection of the fittest' measured for the first time
A difference of one hundredth of a percent in fitness is sufficient to select between winners and losers in evolution.

Related Natural Selection Reading:

Best Science Podcasts 2019

We have hand picked the best science podcasts for 2019. Sit back and enjoy new science podcasts updated daily from your favorite science news services and scientists.
Now Playing: TED Radio Hour

Climate Crisis
There's no greater threat to humanity than climate change. What can we do to stop the worst consequences? This hour, TED speakers explore how we can save our planet and whether we can do it in time. Guests include climate activist Greta Thunberg, chemical engineer Jennifer Wilcox, research scientist Sean Davis, food innovator Bruce Friedrich, and psychologist Per Espen Stoknes.
Now Playing: Science for the People

#527 Honey I CRISPR'd the Kids
This week we're coming to you from Awesome Con in Washington, D.C. There, host Bethany Brookshire led a panel of three amazing guests to talk about the promise and perils of CRISPR, and what happens now that CRISPR babies have (maybe?) been born. Featuring science writer Tina Saey, molecular biologist Anne Simon, and bioethicist Alan Regenberg. A Nobel Prize winner argues banning CRISPR babies won’t work Geneticists push for a 5-year global ban on gene-edited babies A CRISPR spin-off causes unintended typos in DNA News of the first gene-edited babies ignited a firestorm The researcher who created CRISPR twins defends...