Final answer:
Microevolution refers to gradual genetic shifts found among human populations. These shifts can be caused by factors such as genetic drift and gene flow. They result in small-scale changes in the genetic structure of a population over time.
Step-by-step explanation:
The gradual genetic shifts found among human populations are called microevolution. These are small-scale changes in the genetic structure of a population over time. They can be caused by various factors such as genetic drift, gene flow, mutation, nonrandom mating, and environmental variances. For example, genetic drift refers to the random change in allele frequencies that occurs in a small population. If a small number of parents produce just a few offspring, the allele frequencies in the offspring may differ, by chance, from the allele frequencies in the parents. Another factor is gene flow, which is the process in which genes flow from one population to another. This can occur through migration, trade, and other forms of cultural exchange. It can introduce new genetic material into a population and lead to genetic shifts.