Virtual Critters Thrive, Evolve in Online World

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This gives the organisms on Terminus a common language, allowing them to form an ecosystem where they interact naturally with each other—although so far that consists mainly of eating each other.

Cannon Plants and Gridlice

On Terminus, cannon plants make up the bottom of the food chain. A thud and a puff of smoke come from these plants each time they launch a seed into the air from their funnel-shaped leaves.

These explosions often set off a flurry of activity, as creatures known as gridlice and gridbirds flock to the seeds, their sole source of food.

The gridlice resemble horseshoe crabs, with flat, black, rounded heads and pointy gray tails dragging behind as they crawl around on the sand.

Their competitors, the gridbirds, resemble the iconic birds on cuckoo clocks, except they're neon green and have red beaks. The birds hang still in the air and flit about once in a while.

If one of the seeds escapes the feeding frenzy, it can grow into a new cannon plant, helping the species spread.

The ecosystem has just a few simple rules that drive these interactions.

The basic goal was "to implement the simplest possible features of an organism in a way that still allowed flexible and varied behavior," Hart said.

So the creatures have limits, such as what they can eat, how fast they can move, and how high they can jump or fly.

And "we decided we wanted some kind of conservation of energy," Hart said.

Each seed contains a certain amount of fuel, for example. When a gridbird or gridlouse eats a seed, it uses some of that energy to stay alive and to reproduce.

But even with such simple constraints, putting a bunch of different species together can give rise to some surprisingly complex behavior.

"The gridbirds subsist on the same diet as the gridlice," Hart said during a virtual tour of Terminus.

"Since I've introduced [the gridbirds], they've basically chased the lice out of several regions they used to dominate."

Natural Selection

While the gridlice eat and reproduce and the cannon plants spread across the artificial landscape, their basic forms don't change much over time.

So self-employed computer programmer Holden Robbins—through his avatar Pagan Bishop—is working on creatures that can evolve quickly. (Related: "Virtual Life-Forms Mutate, Shedding Light on Evolution" [May 7, 2003].)

These creatures, called Basic Evo Objects, start as plain round blobs that slink around the land. When they reproduce, they can randomly generate an offspring that's a different color—purple instead of green, for example, or with a red ring.

Rather than eating seeds, the creatures chase people's avatars. When they hit one, they shout, "Yay! I got you!" and receive a boost of energy.

These creatures can also evolve surprising behavior, Robbins said.

"At one point I had a bunch of them that would team together and throw [avatars]."

But like an invasive species in a new land, they can get out of control.

"We tend to not leave them unattended so that we don't cause problems," Robbins said. "Sometimes they seem to take off and crash the place."

Hunter avatars occasionally wander into the habitat, he added, especially from a French-language dance club on the plot next door.

"They like to come over and shoot [the creatures] and kill them off."

But some of the Basic Evo Objects escape by evolving to be nearly transparent.

It's natural selection "at its best," Robbins said.

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