Nowak adapted a branch of mathematics known as graph theory, which makes it possible to study networks, to analyze how cancer arises in these local neighborhoods. "Our tissue is actually organized to delay the onset of cancer," he said.
Pockets of intestinal cells, for example, can only hold a few cell generations. That lowers the chances that any one will turn cancerous. All the cells in each pocket are descended from a single stem cell, so that there's no competition between lineages to take over the pocket.
As Nowak developed this neighborhood model, he realized it would help him study human cooperation. "The reality is that I'm much more likely to interact with my friends, and they're much more likely to interact with their friends," Nowak said. "So it's more like a network."
In experiments conducted by other scientists with people and animals, Nowak's mathematical models seem to fit. Reputation has a powerful effect on how people play games. People who gain a reputation for not cooperating tend to be shunned or punished by other players. Cooperative players get rewarded.
"You help because you know it gives you a reputation of a helpful person, who will be helped," Nowak said. "You also look at others and help them according to whether they have helped."
RSS