Which forces typically increase the genetic diversity of a population?

The force that typically increases the genetic diversity of a population is mutation. Mutations are changes in the DNA sequence that can introduce new alleles into a gene pool. These alterations can occur spontaneously or due to environmental factors and can result in new traits that may or may not be beneficial. As mutations accumulate over generations, they provide the raw material for evolution and can enhance a population's adaptability by increasing genetic variation, which is essential for the processes of natural selection and evolutionary change.

In contrast, other forces such as genetic drift primarily lead to changes in allele frequencies through random sampling effects, which can decrease genetic diversity, especially in small populations. Migration, while it can introduce new alleles to a population and thus can contribute to genetic diversity, does not inherently create new genetic variation. Instead, it is the introduction of existing alleles from one population to another. Natural selection acts on existing genetic variation rather than generating new diversity itself. Therefore, mutation stands out as the key mechanism that directly increases genetic diversity in populations.