The bottleneck effect is used to describe an event where a population decreases. One example involves the northern elephant seal. They have a reduced genetic variation due to a population bottleneck humans inflicted on them in the 1890s. Hunting reduced their population size to as few as 20 individuals at the end of the 19th century. Their population has since rebounded to over 30,000, but they have much less genetic variation than a population of southern elephant seals that was not so intensely hunted. Which phrase best explains this change if gene frequency? A) gene flow B) speciation C) genetic drift D) natural selection