Final answer:
The Australopithecus genus includes species like Australopithecus afarensis, dated between 3.9 and 2.9 MYA, and Australopithecus africanus, dated between 2 and 3 MYA. Both species show evidence of bipedalism and arboreal activity, with A. afarensis represented by the famous Lucy fossil.
Step-by-step explanation:
The Australopithecus genus, which includes species such as Australopithecus afarensis and Australopithecus africanus, is significant in our understanding of human evolution. Australopithecus afarensis, famously represented by Lucy, is dated between 3.9 and 2.9 million years ago (MYA). Key features of this species include a brain capacity of 380 to 450 cubic centimeters and evidence of bipedalism despite having long arms and curved fingers, suggesting time spent in the trees.
On the other hand, Australopithecus africanus lived between 2 and 3 million years ago with a brain size of around 500 cubic centimeters, possessing a slender build and bipedal locomotion yet robust arm bones indicating arboreal activities. Other species such as Australopithecus bahrelghazali and Australopithecus garhi have also been discovered, broadening the diversity and complexity of early hominins. All of these species represent important stages in the evolutionary history that would ultimately lead to the genus Homo.