Final answer:
The process that led to the low genetic variability in the northern elephant seals can be termed as a bottleneck.
Step-by-step explanation:
The process that led to the low genetic variability in the northern elephant seals can be termed as a bottleneck. This occurred when the seal population plummeted to just 20 individuals due to intense hunting in the 1890s. Although the population has rebounded since then, their genes still carry the effects of those past generations, resulting in much lower genetic variability compared to the southern elephant seals who did not experience such intense hunting.