Final answer:
Donald Johanson discovered the skeletal remains of an early human ancestor, named Lucy, in Ethiopia in 1974, which was an important find for the study of human evolution.
Step-by-step explanation:
In 1974, Donald Johanson, an American paleoanthropologist, made a significant discovery in Ethiopia during a mapping expedition. He and his colleague found the skeletal remains of an early human ancestor, which included a forearm and a skull in a gully. Upon further investigation, they uncovered more bones and determined that they all belonged to the same hominin. This hominin turned out to be a new species, which they named Lucy after the Beatles song "Lucy in the Sky with Diamonds." About 40 percent of Lucy's skeleton was recovered, which provided invaluable insight into human evolution and became one of the most famous and important fossil finds in the history of paleoanthropology.