Final answer:
Australopithecus afarensis is an extinct hominin species known for evolutionary traits like smaller jaws and teeth compared to apes and larger brain capacity similar to chimps. The famous fossil 'Lucy' is one of the most complete specimens, highlighting characteristics consistent with both tree-dwelling and bipedal movement. This species, along with others in the Australopithecus genus, offers critical information on human evolution.
Step-by-step explanation:
Australopithecus afarensis refers to an extinct hominin species that lived between 3.9 and 2.9 million years ago. This species is significant for numerous features that indicate a trend in human evolution, such as the reduction of the dentition and jaw size compared to apes, while larger than modern humans. A. afarensis had a brain size of 380 to 450 cubic centimeters, similar to that of a modern chimpanzee, and prognathic jaws. One of the most famous specimens of this species is “Lucy”, discovered in the Afar region of Ethiopia and significantly contributing to our understanding of early human evolution.
Lucy (fossil specimen KNM-AL-288) represented a pivotal discovery in paleoanthropology, as it was around 40 percent complete and offered substantial information about the physical characteristics of A. afarensis. The species demonstrated both tree dwelling and bipedal locomotion, which is indicated by traits such as long arms, curved finger and toe bones, alongside a pelvis shape more akin to modern humans.
Other species of the Australopithecus genus include Australopithecus africanus, Australopithecus bahrelghazali, and Australopithecus garhi, each contributing unique insights into the evolutionary history of hominins.