chapter 16

what adaptations help primates live in the trees?

All primates have relatively flexible shoulder and hip joints. These flexible joints are important to some primates for climbing and swinging among branches. Primates have an opposable thumb— a thumb that can cross the palm to meet the other fingertips. Opposable thumbs enable primates to grasp and cling to objects, such as the branches of trees. All these adaptations help primates live in the trees.

What features distinguish anthropoids from strepsirrhines?

Features that distinguish anthropoids from strepsirrhines are as follows: 1. Anthropoids have more complex brains than strepsirrhines. 2. Anthropoids are also larger. 3. Anthropoids have different skeletal features, such as a more or less upright posture, than strepsirrhines.

What evidence supports the idea that H. habilis was an ancestor of H. erectus?

Radiometric dating indicates that H. habilis lived between about 1.5 and 2.5 million years ago. It is the earliest known hominid to make and use stone tools. Some anthropologists propose that a H. habilis population gave rise to a new species about 1.5-1.8 million years ago. This new hominid species was called Homo erectus, which means "upright human." H. erectus had a larger brain and a more humanlike face than H. habilis. These evidences supports the idea that H. habilis was an ancestor of H. erectus.

Why was the development of bipedalism a very important event in the evolution of hominids?

The development of bipedalism was a very important event in the evolution of hominids because in order to move efficiently on the ground while avoiding predators, it was helpful for the hominoids to be bipedal, meaning able to walk on two legs. In addition to increased speed, walking on two legs leaves the arms and hands free for other activities, such as feeding, protecting young, and using tools. Therefore, hominoids with the ability to walk upright probably survived more successfully on the ground.

hominid

a group of bipedal primates that includes modern humans and their direct ancestors.

hominoid

a group of primates that can walk upright on two legs; includes gorillas, chimpanzees, bonobos, and humans.

bipedal

ability to walk on two legs; leaves arms and hands free for other activities such as hunting, protecting young, and using tools.

Neandertal

archaic Homo Sapiens that lived from 35,000 to 100,000 years ago in Europe, Asia, and the Middle East; had thick bones and large faces with prominent noses and brains at least as large as those of modern humans.

australopithecine

early African hominid, genus Australopithecus, that had both apelike and humanlike characteristics.

primates

group of mammals including lemurs, monkeys, apes, and humans that evolved from a common ancestor; shared characteristics include a rounded head, a flattened face, fingernails, flexible shoulder joints, opposable thumbs of big toes, and a large, complex brain.

anthropoid

humanlike primates that include New world monkeys, Old World monkeys, and hominoids.

prehensile tail

long muscular tail used as a fifth limb for grasping and wrapping around objects; characteristic of many New World monkeys.

Cro-magnon

modern form of Homo sapiens that spread throughout Europe between 35,000 to 40,000 years ago; were identical to modern humans in height, skull and tooth structure, and brain size.

opposable thumb

primate characteristic of having a thumb that can cross the palm and meet the other fingertips; enables animal to grasp and cling to objects.