Populations that remain consistentl

Populations that remain consistently small experience a third important effect. Traits under significant selection in large populations, where large numbers of events occur consistently, encounter neutral evolution in small populations, where the small sample of events does not permit a consistent correlation between reproductive success and traits to emerge. Selection can discriminate smaller differences in functional traits in larger populations, differences that would be neutral in smaller populations. In other words, a mixture of natural selection and random processes drives the evolution of all genes and traits. Functionality and neutrality are dependent on situation: sometimes selection dominates, sometimes randomness.