"Since the discovery of the fossil dubbed Lucy 42 years ago this month, paleontologists have debated whether the 3 million-year-old human ancestor spent all of her time walking on the ground or instead combined walking with frequent tree climbing." Source: Science Daily.
"... Analysis of the partial fossilized skeleton, the investigators say, shows that Lucy's upper limbs were heavily built, similar to champion tree-climbing chimpanzees, supporting the idea that she spent time climbing and used her arms to pull herself up."
Note: "[Lucy] weighed about as much as the average 2nd grader and stood about three-and-a-half feet tall," according to the New York Times. If it's true that she was a tree-climber, then it sounds like she was just another kind of monkey. Lucy, however, has been classified as an Australopithecus Africanus, one of dozens of Australopithecus species which evolved around four million years ago. According to current theories, "the genus Homo [evolved] from Australopithecus at some time after three million years ago." (Wikipedia).