The Evolve tab determines whether offspring can differ from their parents, how frequently mutations occur, and which of the four genetic traits are eligible to change across generations.
Mutation controls
| Setting | Type | Range | Default | Description |
|---|
| Enable Mutation | Checkbox | — | On | Master toggle. When off, offspring are genetic clones of their parent regardless of individual gene toggles. |
| Mutation Rate | Slider | 0 – 0.5 (step 0.01) | 0.15 | Probability (per enabled gene, per reproduction event) that a gene value mutates. 0.15 means each enabled gene has a 15% chance of changing. |
| Mutation Strength | Slider | 0.01 – 0.5 (step 0.01) | 0.20 | Range of a single mutation. The actual change is (random() - 0.5) × mutationStrength, so 0.20 means a shift between −0.10 and +0.10 per event. |
Mutation Strength above 0.4 causes rapid random drift. Gene values can swing far from their initial range within a few generations, potentially destabilizing all species simultaneously rather than producing directed selection pressure.
Per-gene toggles
Each gene can be individually frozen. A frozen gene is still inherited by offspring — it just never receives a mutation delta.
| Gene | Default Toggle | What freezing it does |
|---|
| Speed Gene | On | Locks movement speed at its initialized value. All speed variation across organisms reflects Starting Size and Organism Speed slider values only. |
| Aggression Gene | On | Locks hunt/flee bias at its initialized value. Predation behavior is fixed; ecological balance comes entirely from food supply and size dynamics. |
| Efficiency Gene (metabolism) | On | Locks metabolic rate at its initialized value. Energy consumption per unit time cannot evolve; organisms neither become more nor less efficient feeders. |
| Perception Gene (sight range) | On | Locks perception radius at its initialized value. Organisms cannot evolve better or worse awareness of nearby food, prey, or predators. |
Freeze the Speed Gene and Aggression Gene together to isolate Efficiency and Perception evolution. This lets you study how metabolic optimization and sensory range co-evolve without the confounding effect of arms races in raw speed or aggression.
Reproduction mutation logic
When an organism reproduces:
- Each offspring inherits the parent’s exact gene values as a baseline.
- If Enable Mutation is on, each enabled gene is evaluated independently:
- A random number in
[0, 1) is drawn.
- If it is less than
mutationRate, the gene mutates by ±(random() × mutationStrength).
- Disabled genes skip step 2 entirely — they pass through unchanged.
For each enabled gene:
if random() < mutRate:
gene += (random() - 0.5) * mutStr