Final answer:
People in 'Down to a Sunless Sea' and 'The Narrative of Arthur Gordon Pym' resorted to cannibalism due to extreme hunger and lack of food, highlighting survival instincts in dire situations.
Step-by-step explanation:
The characters in both Down to a Sunless Sea and The Narrative of Arthur Gordon Pym resorted to cannibalism out of extreme necessity due to the harsh conditions at sea and in the new colonies, where food sources were scarce or wholly depleted.
In scenarios of life and death, such dire straits drove these individuals to perform acts that would normally be considered unthinkable, including consuming vermin and, ultimately, deceased humans to sustain their own lives.
Famines, diseases, and harsh living conditions contributed to these extreme measures, revealing the primal instinct for survival that can arise in humans when faced with extraordinary and desperate situations.