Which of the following is a key technique used in physical anthropology?

DNA analysis is a key technique in physical anthropology because it allows researchers to study genetic variation and evolutionary relationships among different populations and species. This method provides insights into how humans and other primates are related, tracing lineage and understanding migration patterns over time. By analyzing DNA, anthropologists can explore aspects such as genetic markers for disease, population genetics, and ancestry, which are crucial for understanding human evolution and adaptation.

Other techniques, while useful, do not primarily focus on the biological aspects that physical anthropology emphasizes. For instance, qualitative interviews and textual analysis are more aligned with cultural or social anthropology, focusing on human behavior and cultural narratives, while field surveys can be useful in ecological or archaeological contexts but do not specifically target genetic or physical characteristics.