Final answer:
The allusion to Adam in "A Sound of Thunder" creates a serious tone by highlighting the weighty consequences of time travel and its impact on history.
Step-by-step explanation:
The biblical allusion to Adam in the passage from "A Sound of Thunder" helps create a serious tone by emphasizing the potentially catastrophic consequences of time travel. Travis compares the killing of a prehistoric man to the slaying of some of Adam's grandchildren, suggesting that one small act can have far-reaching effects on the course of history, much like Adam's descendants in the Bible are integral to the unfolding narrative of humanity.