Evolution

There have been a number of attempts to design games about evolution, but none seem to have hit the nail on the head. They are either tedious or not really about evolution. Unlike many other design problems, the verb set here seems to be obvious: The player must select phenotypes to produce a fitter species. The core problem, it seems to me, lies in the set of phenotypes presented to the player. The problem is complicated by the unavoidable interrelationships among many of the phenotypes. My first decision was to limit the game to land vertebrates; this greatly reduces the number of phenotypes the player has to deal with, and it concentrates on the kind of animals most people are familiar with. After some work, I came up with a design using one set of phenotypes and another set of genotypes. Here is the phenotype set:

  • Speed: Fleetness of foot

  • Agility: Ability to jump and change direction quickly

  • Metabolic efficiency: Caloric requirements per kilogram of body weight

  • Digestive efficiency: The efficiency of extracting nutrients from food sources

  • Digestive range: Types of foods digestible

  • Weight

  • Height

  • Armor: Defensive apparatus such as horns, scales, and so on

  • Weaponry: Teeth, claws, and so on

  • Sensory acuity: How good the eyes, ears, and nose are

  • Social intelligence: Ability to cooperate with others in the same species

The set of genotypes is as follows:

  • Musculature: Overall strength

  • Cerebellar size: Fineness of control of musculature

  • Muscular efficiency: Power output per kilogram of muscle

  • Digestive tract size: Directly affects digestive efficiency

  • Armor

  • Weaponry

  • Sensory

  • Social intelligence

You will note that many of the genotypes match closely with phenotypes. However, there's a trick: Each genotype contributes positively or negatively to several phenotypes. For example, musculature increases speed, maneuverability, and agility, but it also increases weight and decreases metabolic efficiency. If you build a carnivore with lots of strengths (say, plenty of speed, maneuverability, agility, weaponry, sensory acuity, and social intelligence), then the poor thing will be huge and have monstrous caloric requirements; it'll starve if it doesn't eat at least a cow a day.

So here's how the game works: At the outset of the game, early evolution has produced two competing biochemistries, one controlled by the player, the other by the computer. Each of these biochemistries has produced just two animals: one herbivore and one carnivore. Although the biochemistries are somehow incompatible, they both can eat the same plants and grasses, and the carnivores can digest the meat of both kinds of animal. In other words, there are two evolutionary teams: the player's critters and the computer's critters.

The environment in which the players compete is a mix of grasslands, savannah, and forest. The two teams have the same set of genes for corresponding creatures, and the overall system is in balance with each creature pursuing an environmentally stable strategy. However, all four critters are optimized for life in the grasslands. In other words, there are just cows and lions. Each species consists of a certain number of individuals.

The player's basic verb is "speciate," which splits a species into a main group, which is unchanged, and a small splinter group of 100 individuals, whose genes the player can alter as part of the speciation process. However, the player can change only a single gene for each speciation act, and the player can speciate a species only when it has at least 1000 individuals. The player also gets to name the new species.

The new species must now compete in the environment against all the other species. Critters play no favorites they'll happily wipe out another species on the same side if it's to their advantage. This is not necessarily bad; the player wants to set up a healthy ecosystem with herbivores providing food for carnivores.

The goal of the game is to achieve maximum gross nutrient extraction in a specified number of turns (shorter for beginning games, longer for advanced games). Maximum gross nutrient extraction means hogging the nutrients provided by the plant life. Those nutrients come in many forms: leafy tissue, seeds, and fruits. Players must therefore build a broad range of herbivores capable of getting all those goodies, but players must also build carnivores to harvest the herbivores better than the computer's carnivores do. Suppose, for example, that at the outset of the game, the plant life is generating 100 units of nutrients every turn, the cows on both sides are each harvesting 20 units of those nutrients (for a total of 40 units), and the lions on both sides are also each harvesting 20 units of cow nutrients each turn (but 20 nutrient units of lion die off each turn, too). This is a stable system; every turn, 20 new units come into the animal system, pass through the cows and lions, and leave the system. The player and the computer each have a score of 40 points. Suppose now that the player creates a new species with better digestive efficiency, and it can now harvest 25 units of plants, but nothing else changes. The player now has 45 points each turn. Of course, the lion populations of both sides will grow slightly to take advantage of the greater number of cows, until the system stabilizes again.

There are all sorts of directions this design could expand in. For example, the simple predator-herbivore model could be vastly expanded into all sorts of other types of critters. How about bugs, or scavengers, or birds? I'd love to introduce changing environments as ways to challenge species, and the occasional giant meteor could certainly inject lots of chaos into the game.



Chris Crawford on Game Design
Chris Crawford on Game Design
ISBN: 0131460994
EAN: 2147483647
Year: 2006
Pages: 248

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