Final answer:
Australopithecus afarensis exhibits significant sexual dimorphism with males being much larger than females, and shows adaptations for both bipedal walking and tree climbing.
Step-by-step explanation:
The question pertains to Australopithecus afarensis, a species of hominid that lived between 3.9 to 2.9 million years ago. A notable characteristic of this species is the presence of sexual dimorphism, which is a significant difference in size or appearance between the sexes of an animal. In Australopithecus afarensis, males were up to 50 percent larger than females. This degree of sexual dimorphism is more pronounced than in modern humans, where males are typically only 15 to 20 percent larger than females. Such dimorphism in Australopithecus afarensis is similar to that seen in modern gorillas and orangutans. Furthermore, Australopithecus afarensis exhibited traits that indicate it was adapted to both bipedalism and arboreal activities. This is evidenced by its pelvic structure, which resembles that of modern humans, and its long arms and curved fingers and toes, which are suited for climbing.