Page 74 of Emergence

All of which raises the question, if evolution didn’t see fit to endow ants with the computational powers of the human brain, how did they become such a dominant presence on the planet? While there’s no single key to the success of the social insects, the collective intelligence of the colony system certainly played an essential role. Call it swarm logic: ten thousand ants-each limited to meager vocabulary of pheromones and minimal cognitive skills collectively engage in nuanced and improvisational problem-solving. A harvester ant colony in the field will not only ascertain the shortest route to a food source, it will also prioritize food sources, based on their distance and ease of access. In response to changing external conditions, worker ants switch from nest-building to foraging to raising ant pupae. Their knack for engineering and social coordination can be downright spooky-particularly because none of the individual ants is actually “in charge of the overall operation. It’s this connection between micro and macro organization that got Deborah Gordon into ants in the first place. “I was interested in systems where individuals who are unable to assess the global situation still work together in a coordinated way,” she says now. “And they manage to do it using only local information.”

Local turns out to be the key term in understanding the power of swarm logic. We see emergent behavior in systems like ant colonies when the individual agents in the system pay attention to their immediate neighbors rather than wait for orders from above. They think locally and act locally, but their collective action produces global behavior. Take the relationship between foraging and colony size. Harvester ant colonies constantly adjust the number of ants actively foraging for food, based on a number of variables: overall colony size (and thus mouths needed to be fed); amount of food stored in the nest; amount of food available in the surrounding area; even the presence of other colonies in the near vicinity. No individual ant can assess any of these variables on her own. (I use