Networking Ability a Family Trait in Monkeys

Jan. 9, 2013 — Two years of painstaking observation on the social interactions of a troop of free-ranging monkeys and an analysis of their family trees has found signs of natural selection affecting the behavior of the descendants.

A family of rhesus macaques. (Credit: Image courtesy of Duke University)


Rhesus macaques who had large, strong networks tended to be descendants of similarly social macaques, according to a Duke University team of researchers. And their ability to recognize relationships and play nice with others also won them more reproductive success.

“If you are a more social monkey, then you’re going to have greater reproductive success, meaning your babies are more likely to survive their first year,” said post-doctoral research fellow Lauren Brent, who led the study. “Natural selection appears to be favoring pro-social behavior.”

The analysis, which appears January 9 in Nature’s Scientific Reports, combined sophisticated social network maps with 75 years of pedigree data and some genetic analysis.

The monkeys are a free-ranging population of macaques descended from a 1938 release of monkeys from India on undeveloped 38-acre Cayo Santiago Island, off the eastern coast of Puerto Rico. They live in a natural setting with little human intervention other than food provisioning, but they do have university students watching them a lot of the time.

Field researchers who had learned to identify each of the nearly 90 monkeys on sight carefully logged interactions between individuals in 10-minute episodes over a two-year span. They compiled four or five hours of data per individual, logging grooming, proximity and aggression.

From that, the team built web-like network maps to analyze pro-social and anti-social interactions. They also looked at the maps for a measure they called “betweenness” — the shortest paths between individuals — and “eigenvector,” a friends-of-friends measure that shows how many friends each friend of an individual has.

“The really ‘popular’ monkeys would have a high eigenvector, or a really big friends-of-friends network,” Brent said. There were also less-popular outliers who had fewer social interactions and a lower eigenvector. “They’re sort of the dorks,” Brent said.

When these measures were then compared to family trees, “a lot of these network measures popped out as having significant heritability,” Brent said. That is, the behaviors seemed to run in families.

“This is really a landmark paper,” said James Fowler, a professor of medical genetics and political science at the University of California-San Diego who studies human social networks, including Facebook, but who was not part of the study. “They’re showing that the positive behaviors which build social networks might be heritable, and that’s consistent with what we’ve been seeing in human studies.”

The analysis of aggression didn’t reveal much heritability, but it did influence reproductive success. At either end of the aggression scale, monkeys who were the most aggressive and those who were the most passive had better reproductive success than the monkeys in the middle.

The team also collected blood samples and did some genetic analysis on two genes in the serotonin system of the monkeys. Variability in the two genes — one that makes serotonin and one that carries it around — was most closely associated with differences in grooming connections between the monkeys.

They chose to focus their genetic analysis on two genes in the serotonin system because there is a lot of literature on that area in humans. Serotonin, a molecule that carries signals between nerve cells, is part of the system acted on by antidepressant drugs, so it has been widely studied.

“The way that genes can affect behavior is by their influence on neural circuits,” said Michael Platt, director of the Duke Institute for a Brain Sciences and the Center for Cognitive Neuroscience. “We know that neural circuits for a variety of things like social behavior, food and mood are under the influence of serotonin signaling, in both humans and monkeys.”

Genes by themselves don’t determine your social standing, Platt added. But social success comes from some combination of social skills and temperament, which appear to have a genetic basis.

“We can see that some of these behaviors have a genetic basis, from what we know of the pedigrees and the network map,” Brent said. “But we’ve only scratched the surface of figuring out which specific genes are associated with each behavior.”

Fowler said the article is especially interesting coming on the heels of a study in Nature last year that showed hunter-gatherer networks are not very different from those in modernized human societies. “So now the conversation is about where to draw the line — how far back did our networks evolve?” Fowler asked. “This paper suggests it may have been a common ancestor with macaques.”

Platt’s group recently won an additional five years of funding from the National Institute of Mental Health to continue and expand the study. Social network observations are now being done on other troops of monkeys on the island and the blood that has been collected will be subjected to further genetic testing.

Having 75 years of family history, combined with the latest genetic tools and a lot of observational data, is going to open up all sorts of new questions, Platt said. “This is just the first two genes,” he said. “We’ll hopefully be moving on to sequence the entire genome of each animal” to find even more associations.

“This is the first major part of what will hopefully be a very big puzzle,” Brent said.


Story Source:

The above story is reprinted from materials provided byDuke University.

Note: Materials may be edited for content and length. For further information, please contact the source cited above.

Journal Reference:

  1. Lauren J. N. Brent, Sarah R. Heilbronner, Julie E. Horvath, Janis Gonzalez-Martinez, Angelina Ruiz-Lambides, Athy G. Robinson, J. H. Pate Skene, Michael L. Platt. Genetic origins of social networks in rhesus macaques.Scientific Reports, 2013; 3 DOI: 10.1038/srep01042
Duke University (2013, January 9). Networking ability a family trait in monkeys. ScienceDaily. Retrieved January 12, 2013, from

How Computation Can Predict Group Conflict: Fighting Among Captive Pigtailed Macaques Provides Clues

ScienceDaily (Aug. 13, 2012) — When conflict breaks out in social groups, individuals make strategic decisions about how to behave based on their understanding of alliances and feuds in the group.

Researchers studied fighting among captive pigtailed macaques for clues about behavior and group conflict. (Credit: iStockphoto/Natthaphong Phanthumchinda)

But it’s been challenging to quantify the underlying trends that dictate how individuals make predictions, given they may only have seen a small number of fights or have limited memory.

In a new study, scientists at the Wisconsin Institute for Discovery (WID) at UW-Madison develop a computational approach to determine whether individuals behave predictably. With data from previous fights, the team looked at how much memory individuals in the group would need to make predictions themselves. The analysis proposes a novel estimate of “cognitive burden,” or the minimal amount of information an organism needs to remember to make a prediction.

The research draws from a concept called “sparse coding,” or the brain’s tendency to use fewer visual details and a small number of neurons to stow an image or scene. Previous studies support the idea that neurons in the brain react to a few large details such as the lines, edges and orientations within images rather than many smaller details.

“So what you get is a model where you have to remember fewer things but you still get very high predictive power — that’s what we’re interested in,” says Bryan Daniels, a WID researcher who led the study. “What is the trade-off? What’s the minimum amount of ‘stuff’ an individual has to remember to make good inferences about future events?”

To find out, Daniels — along with WID co-authors Jessica Flack and David Krakauer — drew comparisons from how brains and computers encode information. The results contribute to ongoing discussions about conflict in biological systems and how cognitive organisms understand their environments.

The study, published in the Aug. 13 edition of theProceedings of the National Academy of Sciences, examined observed bouts of natural fighting in a group of 84 captive pigtailed macaques at the Yerkes National Primate Research Center. By recording individuals’ involvement — or lack thereof — in fights, the group created models that mapped the likelihood any number of individuals would engage in conflict in hypothetical situations.

To confirm the predictive power of the models, the group plugged in other data from the monkey group that was not used to create the models. Then, researchers compared these simulations with what actually happened in the group. One model looked at conflict as combinations of pairs, while another represented fights as sparse combinations of clusters, which proved to be a better tool for predicting fights. From there, by removing information until predictions became worse, Daniels and colleagues calculated the amount of information each individual needed to remember to make the most informed decision whether to fight or flee.

“We know the monkeys are making predictions, but we don’t know how good they are,” says Daniels. “But given this data, we found that the most memory it would take to figure out the regularities is about 1,000 bits of information.”

Sparse coding appears to be a strong candidate for explaining the mechanism at play in the monkey group, but the team points out that it is only one possible way to encode conflict.

Because the statistical modeling and computation frameworks can be applied to different natural datasets, the research has the potential to influence other fields of study, including behavioral science, cognition, computation, game theory and machine learning. Such models might also be useful in studying collective behaviors in other complex systems, ranging from neurons to bird flocks.

Future research will seek to find out how individuals’ knowledge of alliances and feuds fine tunes their own decisions and changes the groups’ collective pattern of conflict.

The research was supported by the National Science Foundation, the John Templeton Foundation through the Santa Fe Institute, and UW-Madison.

Story Source:

The above story is reprinted from materials provided byUniversity of Wisconsin-Madison.

Journal Reference:

  1. Bryan C. Daniels, David C. Krakauer, and Jessica C. Flack. Sparse code of conflict in a primate society.Proceedings of the National Academy of Sciences, 2012; DOI: 10.1073/pnas.1203021109

University of Wisconsin-Madison (2012, August 13). How computation can predict group conflict: Fighting among captive pigtailed macaques provides clues. ScienceDaily. Retrieved August 15, 2012, from