This lesson explores bipedalism, the defining movement pattern shared by hominins, and the anatomical evidence that helps scientists identify it. Understanding how early hominins walked provides a foundation for interpreting fossils and reconstructing ancient behavior.
A hominin is a species in the direct lineage to humans. The group includes species from the genera Homo, Australopithecus, Paranthropus, and Ardipithecus. Hominids include modern and extinct great apes—humans, gorillas, chimpanzees, and orangutans—and their ancestors. Although these terms have changed in use over time, these are the definitions used in this unit.
All flashcards
What is a hominin?
A species considered to be in the direct lineage to humans, including members of genera such as *Homo*, *Australopithecus*, *Paranthropus*, and *Ardipithecus*.
What is the difference between the stance leg and the step leg?
The stance leg is on the ground and supports the body; the step leg moves forward during a stride.
What is the valgus angle?
The inward angle of the femur that brings the knees and feet under the center of the pelvis, helping a biped balance.
How do the foot arch and aligned big toe help walking?
The arch supports and transmits weight, while a big toe aligned with the other toes helps the foot bear weight and push off.
Why are the Laetoli footprints important?
They preserve a trail of early bipedal footprints, probably made by *Australopithecus afarensis*, showing a striding gait about 3.5 million years ago.
Quiz questions
What evidence from *Orrorin tugenensis* has been used to argue that it walked bipedally?Answer: Femoral features suggest the leg supported the upper body's weight during movement.
Why have some researchers questioned whether *Sahelanthropus tchadensis* was bipedal?Answer: The position of its foramen magnum has been interpreted as inconsistent with the head held directly above the spine.
What locomotor pattern is suggested by the combination of traits in *Ardipithecus ramidus*?Answer: Bipedal walking on the ground and quadrupedal movement in trees.
What do the anatomical traits of *Australopithecus afarensis* suggest about its movement?Answer: It walked bipedally on the ground and also spent time climbing in trees.
What was the function of the sagittal crest in robust australopithecines?Answer: It provided attachment area for large temporalis muscles used in powerful chewing.
Based on Introduction to Anthropology by Jennifer Hasty, David G. Lewis, Marjorie M. Snipes (OpenStax), licensed CC BY 4.0. Adapted into a summary, flashcards and quizzes.