Wednesday, November 14, 2007

The Hobbesian world of the Mormon cricket, revealed in the NYT's science story about swarming

"From Ants to People, an Instinct to Swarm" is the title of the NYT story summarizing current research on the physics, biology and mathematics of swarming, which happens throughout the animal kingdom and may even happen among the cells in our brains.
If you have ever observed ants marching in and out of a nest, you might have been reminded of a highway buzzing with traffic. To Iain D. Couzin, such a comparison is a cruel insult — to the ants.

Americans spend a 3.7 billion hours a year in congested traffic. But you will never see ants stuck in gridlock.

Army ants, which Dr. Couzin has spent much time observing in Panama, are particularly good at moving in swarms. If they have to travel over a depression in the ground, they erect bridges so that they can proceed as quickly as possible.
It's a fascinating article, especially the material about how computer scientists are studying swarming by creating simple rules, such as maintaining a certain distance from your neighbor, that can be used to create realistic computer models of highly complex swarm behavior.

Swarming is a beautiful example of complexity emerging from simplicity. Some of the simple rules apply to many species. Some are highly specific, such as this dramatic rule that applies to the Mormon cricket in Utah.
Mormon crickets will sometimes gather by the millions and crawl in bands stretching more than five miles long. Dr. Couzin and his colleagues ran experiments to find out what caused them to form bands. They found that the forces behind cricket swarms are very different from the ones that bring locusts together. When Mormon crickets cannot find enough salt and protein, they become cannibals.

“Each cricket itself is a perfectly balanced source of nutrition,” Dr. Couzin said. “So the crickets, every 17 seconds or so, try to attack other individuals. If you don’t move, you’re likely to be eaten.”

This collective movement causes the crickets to form vast swarms. “All these crickets are on a forced march,” Dr. Couzin said. “They’re trying to attack the crickets who are ahead, and they’re trying to avoid being eaten from behind.”
Kind of makes that famous statement by Thomas Hobbes that life in a state of nature without a social contract is "solitary, poor, nasty, brutish and short" seem like a huge understatement.

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