BIOLOGY / EVOLUTION

Populations change
across generations.

The environment favors some inherited traits. Chance decides which parents leave the next generation.

FIG. 01 · THE BEETLE COHORT100 individuals
Starting cohortSpace / → to step
Dark / striped 5050 Pale / spotted
Generation 0 · 50 dark / 50 pale
GENERATION 0

Selection biases the odds.
It does not dictate the result.

Relative survival weights: . The next cohort's expected share is ; 100 random offspring draws produce the actual count.

Dark parents produce dark offspring; pale parents produce pale offspring. A new generation replaces the entire tray. Individuals never change traits to match the ground.

Dark trait frequency latest 41 cohorts
1000

At zero selection, finite-population drift still changes frequencies. Even an advantageous trait can disappear.