Question

you are on an archaeological dig in africa when you find a collection of stone tools along with several skeletons in a cave. these bipedal skeletons date to about 3.5 million years ago and show no evidence of a partially opposable toe. measurements indicate the brains would have been a little less than a third of the volume of modern humans. the teeth found on these skeletons look more like those of an ape than those of a human. your skeletal discovery is most likely which of the following?

sahelanthropus tchadensis

homo erectus

australopithecus afarensis

ardipithecus ramidus

Explanation:

• Sahelanthropus tchadensis: Lived around 7 million years ago, so the 3.5 - million - year - old date in the problem does not match.
• Homo erectus: Had a larger brain (about 700 - 1200 cc, while modern human brain is about 1300 - 1400 cc, so more than a third of modern human brain volume). Also, their teeth were more human - like compared to the description in the problem.
• Australopithecus afarensis: Lived approximately 3.9 - 2.9 million years ago (fits the 3.5 - million - year - old date). Had a brain volume of about 380 - 450 cc (modern human brain is about 1300 - 1400 cc, so less than a third). Had ape - like teeth. Was bipedal and had a non - opposable toe (no evidence of a partially opposable toe as in some other early hominins).
• Ardipithecus ramidus: Lived around 4.4 million years ago, so the date in the problem does not match well.

Answer:

Australopithecus afarensis