Final answer:
The species Australopithecus anamensis is dated to 4.2 million years ago, pre-dating Australopithecus afarensis which lived between 3.9 and 2.9 million years ago. These early hominins are critical for understanding human evolution, showing trends like reduced dentition and the shift towards bipedalism.
Step-by-step explanation:
Australopithecus Anamensis Timeline
The species Australopithecus anamensis is understood to have lived approximately 4.2 million years ago. As members of the genus Australopithecus, this species is vital in the study of human evolution. Their existence represents an important phase in our evolutionary history. Australopithecus afarensis, which followed A. anamensis, lived between 3.9 and 2.9 million years ago, displaying significant evolutionary changes. For example, A. afarensis exhibited a reduction in the size of dentition and jaw compared to its ancestors. The species was more bipedal, as suggested by pelvic morphology resembling that of modern humans, despite having an endocranial capacity of around 400 cc, similar to that of a chimpanzee.
Another prominent Australopithecus species is Australopithecus africanus, which existed between two and three million years ago. A. africanus presented traits such as bipedality along with robust arm bones, indicating the likelihood of spending time in trees. The genus Australopithecus encompassed both gracile and robust forms, with species such as Paranthropus robustus falling into the latter category, surviving until roughly one million years ago.
The Australopithecus species, including anamensis, are central to our understanding of the early hominin lifestyle and the evolutionary path leading to modern humans. Their fossil records offer invaluable insights into the morphological adaptations that distinguished them from apes and set the stage for the emergence of the genus Homo.