Natural selection

Owns no trait values itself; it is the rule that ties reproduction and death to how well an individual's traits fit the environment, so populations change without a designer choosing outcomes. Each generation, individuals that find food, avoid predators, and tolerate climate leave more offspring; with heritable variation the trait distribution moves toward fitter values, and when populations split by geography or genetic distance new species can form. Species: ALRE (Early Access 2018) charges energy for movement from skeleton forces and torques, lets creatures eat only within head reach, and defines species by interbreeding within a genetic distance. SimLife (1992) lets players edit genetics and environments and watch evolution. Spore (2008), by contrast, has players design creatures directly and is not natural selection. Inputs: heritable traits, environment, mortality and reproduction. Outputs: changing trait distributions, speciation, extinction.

The player shifts from designer to gardener: setting conditions and watching which bodies and behaviors win. Results surprise and teach, as in finding why the long-necked line died out after an ice age.

• fitness sources (energy budgets, predation, climate tolerance, mate choice)
• generation time relative to play pace
• population size, which sets drift versus selection strength
• speciation rule (genetic distance, geography)
• player interventions such as culling, feeding, catastrophes, and nurseries

• Evolution is too slow to see within a session, so players perceive nothing happening.
• Degenerate optima: populations converge on one exploit body plan and diversity collapses.
• Fitness hidden behind physics is opaque, so players cannot tell why traits win.
• Games that call designed progression evolution set expectations they do not meet; biologists criticized Spore's model.

• Arms races between predator and prey traits.
• Environmental shocks cause extinction and radiation into emptied niches.
• Coupled with food webs, species composition and trait distributions shift together.

• Can learned simulators or GPU-accelerated physics make open-ended evolution fast enough to watch in a session?
• What visualizations let players see selection pressure acting, not just its outcome?