Cutting edge: Eric Bonabeau

December 8, 2000

A fear of ants becomes a fascination as an engineer applies their genius to computers.

As a kid, I was terrified of insects. I remember with retrospective anguish holidays in the south of France, when picnics turned into nightmarish fights against carnivorous wasps and ferocious ants intent on raiding my sandwich. Sometimes, I wonder how on earth I could have gone on to dedicate eight years of my life to social insects.

The transition took place in the early 1990s in Santa Fe, at the foot of the Rocky Mountains, when I was a France Telecom engineer. Meeting Guy Theraulaz at a seminar at the Santa Fe Institute changed my life. Guy, a French scientist who studies division of labour and nest construction in social wasps, introduced me to the amazing world of swarm intelligence, the collective intelligence of social insect colonies. Individually insects may not be capable of much, but collectively, social insects are capable of great things, from building and defending a nest to foraging for food.

For instance, a colony of ants can collectively find out where the nearest and richest food source is located, without any individual ant knowing it. In experiments, a food source was separated from the nest by a bridge with two branches, one longer than the other. The shorter one was most likely to be selected by the colony. This is because ants lay and follow chemical trails: individual ants put down a pheromone, which attracts other ants. The first ants to return to the nest were those that took the shorter path there and back. Nest mates were guided toward the shorter branch, which was the first to be marked with pheromone.

Listening to this story was an epiphany because I saw a powerful computing metaphor. By discovering the shortest path to a food source, the ants collectively solve an optimisation problem using emergent computation.

Back at France Telecom, I applied this insight to a recurrent telecommunications network problem: routing. Routing is needed because most large-scale communications networks are not fully connected for cost effectiveness, so messages have to be guided to reach their destination. I found that by letting virtual ants leave virtual pheromone at the network's nodes or routers, the routes that messages use could be optimised. The virtual ants are small computer programs that are sent through the network, just like messages, except they can modify information at the routers. The technique worked wonders.

Since then, the ant approach has been successfully applied to a number of real optimisation and control problems, from factory scheduling to network routing. It has the advantage of being robust and flexible in response to changing conditions. This crucial property is useful in any real-world context, where things are never static. For example, in a factory when a machine breaks down or demand for products changes, the artificial ants quickly find new production schedules.

Some may think I have cheated by studying virtual insects to get rid of my insect phobia. Well, in parallel with my work at France Telecom, I started a collaboration with Guy Theraulaz, and Jean-Louis Deneubourg of the Universite Libre de Bruxelles, on real social insects. We have a nice division of labour whereby they do the experimental work, with my assistance, and I do the modelling and simulation. After several years of modelling the behaviour of social insects, I have started to understand them better and develop a respect that one day transformed into, well, not love, but tolerance of their presence at picnics.

Eric Bonabeau is chief scientist at Icosystem Corporation, a Boston and Paris-based consultancy dedicated to business model innovation.

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