Chapter 16, Problem 16A

Summary Introduction

Introduction:

Some scientists propose that between 5 and 8 million years ago in Africa, a population that was ancestral to chimpanzees and humans diverged into two lines. One line evolved into chimpanzees and the other line evolved into modern humans. The oldest hominoid fossil appears in about 25 mya at the beginning of Miocene. Hominoids include all nonmonkey anthropoids- the living and extinct gibbons, orangutans, chimpanzees, gorillas, and humans.

Answer to Problem 16A

Correct answer :

The correct answer is option D. Proconsul

Explanation of Solution

Explanation/justification for the correct answer:

Option D. Proconsul - The oldest known hominoid fossils are from the genus Proconsul . They are considered to be the ancestors of apes and humans. They had the smallest brains of the hominoids. Most had freely moving arms and mainly lived on trees. The australopithecines came after the Proconsul .

Hence this is the correct option.

Explanation for incorrect answer:

Option A. A.afarensis - An anthropologist Donald Johanson discovered an australopithecine skeleton named Lucy in Kenya in1974. The first hominins that were truly bipedal were the australopithecines. They were small and had apelike brains and jaws but the teeth and limb joints were humanlike. Lucy was a member of new species A.afarensis which probably lived about 3.2 million years ago.

Hence this is not the correct option.

Option B. A.africanus - The first australopithecine fossils found was the “Taung baby” in Africa. It was called the species Australopithecus africanus, meaning “southern ape from Africa.” They are most likely to have lived between 2.5 and 2.8 million years ago. So they are not considered to be ancestral to apes and humans as they came much later than the Pronconsuls .

Hence this is not the correct option.

Option C. Paranthropus -. This genus includes robust forms of australopithecines ( A. bosei and A. robustus ) different from the smaller and slender forms. These lived between 2.5 and 4.3 million years ago. Hence this is not the correct option.