Vocabulary

prehensile appendage anthropoid primate opposable thumb great ape bipedalism hominid australopithecine human figure 43-16

Primate characteristics are mostly adaptations for a social life in the trees.

Large brain parts relative to size

Primate brains support complex skills, such as using hands, interpreting visual information, interacting socially, and caring for offspring.

Acute color vision

Forward-facing eyes allow binocular vision, depth perception, and skilled movement in three-dimensional space.

Generalist teeth

The variety of teeth permits herbivorous and omnivorous diets.

Communication

Facial and vocal structure enables broad range of expressions and sounds.

Infant care

Infants require prolonged care; reduced litter size permits greater mobility and attention to each young; there is usually one pair of mammary glands on the chest

Communication

Facial and vocal structure enables broad range of expressions and sounds.

Social organization

Many primates live in social groups with complex behaviors among members.

Manual dexterity

Opposable thumbs can touch other four fingers; fingers can grip or manipulate objects; flattened nails protect finger pads.

Social organization

Many primates live in social groups with complex behaviors among members.

Characteristic skeletal structure

Primates can sit upright, cling to trees, or hang from branches; major bones of limbs are like those of earliest mammals, with one upper and two lower bones.

figure 43-17

Anthropoids such as this white-handed gibbon, Hylobates lar, have rotating shoulder and elbow joints. This adaptation enables anthropoids to swing by their arms through trees.

figure 43-17

Anthropoids such as this white-handed gibbon, Hylobates lar, have rotating shoulder and elbow joints. This adaptation enables anthropoids to swing by their arms through trees.

figure 43-18

Humans have certain physical traits that differ markedly from those of the chimpanzee, a modern ape: the jaw, pelvis, spine, feet, and toes.

Anthropoids

The primate lineages that evolved the earliest include lemurs, lorises, and tarsiers. These groups are sometimes referred to as prosimians. The gibbon in Figure 43-17 is one of the anthropoid primates, a group that also includes New World monkeys, Old World monkeys, apes, and humans. Anthropoid adaptations include rotating shoulder and elbow joints and an opposable thumb, which can touch the other fingers. Anthropoids can hold and manipulate objects precisely, as when a chimpanzee peels a banana or when a student holds a pencil. Nonhuman anthropoids also have grasping feet with an opposable big toe.

Humans, apes, and Old World monkeys have a similar dental formula, or number and arrangement of teeth. Each half of the upper and lower mouth includes two incisors, one canine, two premolars, and three molars, as shown in Figure 43-18. Compared to other primates, anthropoids have a more complex brain structure and a larger brain relative to body size.

Orangutans, gorillas, chimpanzees, bonobos, and humans make up the great apes. Chimpanzee and human DNA is so similar that humans are thought to be more closely related to chimpanzees than to any other living primates. DNA and fossil evidence suggests that humans and chimpanzees share a common ancestor that lived about 6 million years ago. Humans, however, did not descend from chimpanzees. Rather, modern apes and humans both descended from an ancestral apelike species.

Modern Humans

Among living mammals, only we humans, Homo sapiens, have the trait of bipedalism (bie-PED'l-IZ-uhm), the tendency to walk upright on two legs. The human skeleton is adapted for bipedalism in several ways, as shown in Figure 43-18.

Essentials of Human Physiology

Essentials of Human Physiology

This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.

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