Final answer:
Naturalist writing differed from realist writing by emphasizing the impact of heredity and environment on characters and by addressing more provocative subjects.
Step-by-step explanation:
In the late nineteenth century, naturalist writing most clearly differed from realist writing of the same period by exploring the influence of heredity and environment on human behavior. Unlike Realism, which focused on depicting everyday life and the struggles of ordinary people with authenticity, Naturalism took this further by emphasizing how characters were shaped by natural and social forces beyond their control. Naturalist writers, influenced by Charles Darwin and Émile Zola, investigated human lives under the lens of pessimistic materialistic determinism, bringing to light more provocative subjects such as prostitution, alcoholism, domestic violence, and the stark realities of human existence.