Answer:
Bottle-neck effect
Explanation:
Bottle neck effect is a type of genetic drift where there is a sharp and gradual reduction of a population due to human activities or environmental events.
Due reduction in the size of the population, there will be reduction in the gene pool therefore leading to little genetic variation.
Just like in the northern elephant seal, human hunting lead to their gradual reduction of their population. This made the elephant population have a little genetic variation between individuals.