How does natural selection primarily occur?

Natural selection primarily occurs as a result of environmental pressures. This process involves individuals within a population having varying traits that can affect their survival and reproduction. When environmental factors—such as climate, availability of resources, predation, or disease—exert pressure on a population, individuals with traits that better suit them to their environment are more likely to survive and reproduce. Over time, these advantageous traits become more common in the population, leading to adaptation.

While random genetic mutations play a role in providing the genetic variation upon which natural selection acts, it is the interaction between these variations and environmental pressures that drives the process of natural selection. Rather than eliminating all weaker individuals, natural selection works on a spectrum, where certain traits are favored in a given context, which may not necessarily equate to the outright elimination of weaker individuals. Artificial breeding, on the other hand, is a human-directed process that does not reflect the natural mechanisms of evolution.