Human evolution gets tested against the evidence embedded in the body itself, as anatomist Alice Roberts works through skeletons, skulls, and living joints to explain why we are built the way we are. She examines the human foot and spine to show what upright walking cost the skeleton, compares jaw and tooth structure across hominin fossils to track the shift toward cooked and processed food, and looks at the mobile human thumb as the anatomical change that made tool use possible. The brain gets its own treatment, with Roberts weighing its size and energy demands against the risks that a larger skull created for childbirth. Throughout, she treats each trait as a trade-off rather than a triumph: an opposable thumb or an upright gait solves one survival problem while creating new vulnerabilities that still show up in modern injuries and ailments. The series stays grounded in physical evidence, handling bones and models on camera rather than relying on narration alone to make its case.