Which process can lead to the emergence of new species?

The emergence of new species, or speciation, often results from mechanisms that alter the genetic structure of populations. Natural selection plays a fundamental role by favoring traits that enhance survival and reproduction in changing environments, potentially leading to divergent evolution when populations adapt to different ecological niches.

Genetic drift, another key mechanism, involves random changes in allele frequencies within small populations, which can lead to significant genetic differentiation over time. When combined, natural selection and genetic drift can contribute to the reproductive isolation necessary for speciation.

In contrast, gene flow, which refers to the exchange of genetic material between populations, usually acts to homogenize genetic differences, making it less conducive to the emergence of new species. Environmental stability does not inherently drive speciation, as stable environments can lead to reduced selective pressures, potentially decreasing the likelihood of divergence.

Therefore, the correct answer acknowledges the synergistic effects of both natural selection and genetic drift in the process of speciation.