What mechanism would most likely result in a population becoming less diverse over time?

Genetic drift is a mechanism that can lead to a reduction in genetic diversity within a population over time. This process often occurs in small populations, where random events can have a disproportionate effect on the gene pool. For example, if a natural disaster occurs and randomly eliminates a portion of the population, the alleles carried by those individuals may be lost from the population entirely, decreasing its genetic variation.

Over generations, this random loss of alleles can accumulate, leading to populations that are less diverse genetically. Unlike mechanisms such as natural selection, which can promote certain traits based on their advantageous impact on survival and reproduction, genetic drift operates purely on chance, resulting in the potential fixation of certain alleles while others are lost. Consequently, the overall genetic variation within the population diminishes, leading to lower diversity.

In contrast, gene flow introduces new alleles into a population, mutation creates new genetic variations, and natural selection can support genetic diversity by favoring beneficial traits. These processes generally help maintain or increase genetic variation rather than reduce it.