Australopithecus, an early hominid.

1. Lucy, a 3.24-million-year-old skeleton, represents the hominid species Australopithecus afarensis.

2. The Laetoli (Tanzania) footprints, more than 3.5 million years old, confirm that upright posture evolved quite early in hominid history.

3. An artist’s reconstruction of what A. afarensis may have looked like.