Northern elephant seals have reduced genetic variation because of a population bottleneck inflicted on them in the 1890's by humans. hunting reduced their population size to 20 individuals at the end of the 19th century. although their population has rebounded to over 30,000 , but their genes still carry the marks of this bottleneck and they have much less genetic variation than a population of southern elephant seals that was not so intensely hunted.
big losses of genetic variation for the small populations are readily caused by
a) gene flow.
b) genetic drift.
c) natural selection.
d) the founder effect.