a. Charles Darwin avoided the subject of human evolution in his writings until 1871, when he published The Descent of Man, twelve years after his On the Origin of Species first presented the theory of evolution by natural selection.

b. The first, and most famous, confrontation between evolutionists and creationists took place in Oxford, England on June 30, 1860, at the annual meeting of the British Association for the Advancement of Science.

c. At that meeting, Thomas Henry Huxley, speaking for Darwin, debated Bishop Samuel Wilberforce, who attacked Darwin's thesis.

d. Though Bishop Wilberforce spoke skillfully, Huxley emerged victorious after humorously turning Wilberforce's dishonest claims into nonsense.

e. This chapter shows that the forces of evolution that operate on other organisms have shaped humanity just as inexorably, and continue to do so today.

a. Humans are in the order Primates (Table 36.1), which includes the monkeys and the apes.

b. Humans are most closely related to apes of the family Pongidae, sharing with them ancestors that lived about 25—20 years ago.

c. The primates evolved during the great adaptive radiation of mammals, around 70—65 million years ago, from the order Insectivora, which currently includes the moles and shrews.

d. The modern tree shrew shares characteristics of both insectivores and primates (Figure 36.1), such as a large brain and a slightly opposable first digit (thumb).

e. Modern shrews eat fruit as well as insects; primates are generally frugivorous or omnivorous.

f. Most primates are adapted to an arboreal life, living on leaves and fruits; a few species such as humans have switched to life on the ground.

g. Many non-primate mammals have highly specialized extremities such as hooves, flippers, and fins.

h. Primates, however, are generalized mammals, with an opposable thumb as an important feature.

i. All primates can use their hands in a power grip (Figure 36.2) for climbing and grasping; others have a precision grip (Figure 36.2) for manipulating objects.

j. The precision grip is a key factor in cultural evolution, since it allowed primates to make and use tools.

k. Primates have very long arms that can rotate freely in several ways (Figure 36.3), a clear advantage for tree-dwellers.

l. The most advanced primates have flat nails instead of claws, leaving a bare, protected, but highly innervated and sensitive working surface at the ends of the digits; this contributed to manual dexterity.

m. Primates lack specialized teeth, a feature associated with their omnivory.

n. Primate eyes are placed for excellent stereoscopic vision with depth perception, and contain not only rods, but cones for color vision, and a fovea that is the point of the clearest vision (Figure 36.4).

o. Areas of the primate brain that deal with information from the eyes and the sensitive hands are enlarged; the olfaction areas are diminished.

p. Upright posture is a feature of all primates; it allows a better view of the surroundings, a wider range of vision, and it also frees limbs for carrying things such as tools and babies.

a. The order Primates is divided into two suborders (Table 36.1), the Strepsirhini and Haplorhini.

b. The Strepsirhini includes the prosimians such as lemures and lorises (Figure 36.5), primitive primates that have wet noses associated with a sharp sense of smell.

c. Most prosimians now live on the island of Madagascar, as their ancestors were probably replaced by better-adapted monkeys.

d. The Haplorhini include the simians (Figure 36.6), which have dry noses that are not so sensitive to smell, and mobile upper lips that allow for a variety of facial expressions.

e. Three Haplorhini families that include the gibbons, apes (chimpanzees, gorillas, and orangutans), and humans all make up the hominids of the superfamily Hominidae.

f. Monkeys arose in the Oligocene epoch, around 40 million years ago, and diverged into New World and Old World clades.

g. The modern New World monkeys are all characterized by broad-nosed platyrrine faces and prehensile tails (Figure 36.7).

h. Continental drift information suggests that New World monkeys could not have occupied South America at the time the continent diverged from Gondwanaland; the South American monkey fauna may have arisen independently from tarsoid primates or by invading the continent from North America via an archipelago.

i. The Old World monkeys include the macaques, baboons, and mangabeys of Africa and tropical Asia.

j. Old World monkeys have catarrhine faces, with snouts and noses pointed downward, and they do not have prehensile tails.

k. The Hominidae arose from the Old World monkeys, as indicated by several features, including a common dental pattern.

l. Late-Oligocene epoch Egyptian fossil beds have yielded fossils of the first hominoids, including Aegyptopithecus zeuxis, possibly the oldest known hominoid, which had teeth very much like those of a modern ape.

m. Sidebar 36.1 covers evolution with regard to populations versus species.

a. Apes differ from monkeys by the lack of a tail, different tooth structure, and more upright posture.

b. Apes move through trees chiefly by brachiation, swinging from branch to branch (Figure 36.8).

c. Larger apes spend much of their time on the ground, and can walk upright, though they are hunched and clumsy due to their pelvis shape (Figure 36.9).

d. Chimpanzees and gorillas move about by knuckle walking, and can thus carry things in their clenched fists.

e. Tropical forests in Africa and Asia gave way to grasslands during the late Oligocene epoch, and the first hominoids moved into a new adaptive zone in the grasslands, changing their diet from leaves and fruits to nuts and roots.

f. These dryopithecene apes lived over a vast area from southern Europe through East Africa, India, and China, and have been identified as the likely ancestors of modern apes.

g. Probably due to their change in diet, dryopithecenes lost the protruding canine teeth of earlier simians, and developed strong, more rounded jaws and heavily enameled teeth (Figure 36.10).

h. Dryopithecenes lived until about 7 million years ago; transitional species existed until 4 million years ago when the first definitive hominids, who walked fully upright, came into existence.

a. A skull of the first known hominid, Australopithecus africanus, was discovered and named in 1924, and it had many of the features of a bipedal hominid: rounded shape, large cranial capacity, rounded jaw, and attachment to the spine in a more central position.

b. Other australopithecene fossils discovered later had similar features, but with protruding jaws and heavy brow ridges that didn't disappear from hominids until much later.

c. Those dated between about 3 and 1.5 million years ago represent two main groups – the shorter, lighter, meat-eating gracile forms and the taller, heavier, vegetarian robust forms (Figures 36.11 and 36.12).

d. Two important adaptations in the australopithecine skeleton helped give rise to modern humans: increased brain size, and changes in the pelvis and leg bones to favor bipedalism and a fully upright posture, which was also suited for climbing (Figure 36.13).

e. An extensive series of australopithecine fossils about 4 million years old was unearthed in the Afar Triangle (Figure 36.14) during the 1970s; these fossils clearly showed that hominids of that time were bipedal and stood fully upright.

f. In 1992, fossils dated 4.4 million years old were discovered and have pushed the hominid line back farther, almost to the point where it branched off from the great apes.

g. These older fossils defined a species, Ardipithecus ramidus, known as "the most apelike hominid ancestor known."

h. The hominid and ape clades thus diverged sometime between 7 million and 5 million years ago.

a. Human evolution is characterized by anatomical changes and by the development of an extensive culture that is represented in fossils by bones and tools.

b. Each collection of tools and other artifacts is called a tradition or an industry, and is named for a locality where typical remains are found.

c. In Olduvai Gorge, Tanzania, Louis and Mary Leakey discovered primate stone tools (Figure 36.15) and bones that seemed associated with them, and named a new species, Homo habilis ("handy man").

d. In Kenya, Richard Leakey discovered a series of fossils that were associated with a larger brain capacity and a more advanced tradition of tools than those found with H. habilis; a new species, Homo rudolfensis, was named for this group.

e. Currently, four types of hominids are thought to have coexisted in Africa for a period of about a million years.

a. About 1.5—1 million years ago, H. habilis was replaced by Homo erectus (Figure 36.16).

b. The first discovered H. erectus fossils were found in Java in 1891 and were originally named Java man or Pithecanthropus erectus, meaning "ape man that walks erect."

c. H. erectus individuals, which were widely distributed in Europe, Africa, and the Near East, were about 1.5 meters tall, with a skeleton similar to the modern human, but with smaller brains, massive, primitive teeth, and heavy eyebrow ridges.

d. The erectus people left clear records of their culture; they were omnivorous hunters and gatherers, who used hand-axes and other stone tools while existing during a long period, the Lower Paleolithic (Old Stone Age).

e. H. erectus is associated with the oldest (Abbevillian) culture, characterized by the production of both core and flake tools (Figure 36.17).

f. A core tool is made by chipping pieces off a large flint rock; the remains make the tool and the pieces that are chipped off can be fashioned into flake tools.

g. The erectus humans were probably nomads who roamed in small groups but maintained base camps, and they used fire at least a half-million years ago.

h. Early erectus humans probably went naked and lived in the open, but a series of later ice ages (Figure 36.18) probably caused them to move into caves and use animal skins for clothes.

i. Evidence indicates that H. erectus probably used a kind of rudimentary language, an adaptation that offered selective advantages for people dependent on cooperative activities like hunting, traveling in groups, and handing down traditions and information to new generations.

a. Between 250,000 and 150,000 years ago, H. erectus was replaced as the dominant hominid by our own species, H. sapiens, the earliest fossils of which are named H. sapiens neanderthaliensis, after the Neander valley in Germany where they were found.

b. The Neanderthals had large cranial capacities and generally resembled modern humans below the neck, but their facial features in some cases included a markedly receding chin, heavy brow ridges, and a sloping forehead (Figure 36.19), possibly a regional difference attributable to climate.

c. The period of Neanderthal dominance was from about 150,000 to 30,000 years ago, when humans shared the cool, temperate Mediterranean region with mammals such as elephants, hippopotamuses, rhinoceroses, saber-toothed tigers, woolly mammoths, and woolly rhinoceroses.

d. Neanderthals replaced the Abbevillian tradition in toolmaking with the Acheulian, and then by the Mousterian industry, as delicately shaped tools such as scrapers and spear points were made.

e. Neanderthals must have hunted with stone-tipped spears and possessed knives to kill and butcher animals; they also used fire for cooking and warmth.

f. Neanderthals carefully buried their dead and apparently had rites concerning life and death.

a. Three models currently are in contention for explaining the transition between Neanderthals and modern humans:

b. Modern molecular evidence has not been able to resolve this controversy, though the great diversity of histocompatibility genes is inconsistent with evolution from a very small group.

c. Better dating techniques have shown that modern humans lived at the same time as Neanderthals and the two groups may have coexisted for thousands of years.

d. Physical evolution in humans has not stopped, but has become secondary to cultural evolution, as only small genetic differences currently exist among contemporary groups.

e. The first modern sapiens are known as Cro-Magnons, from the cave in southern France where their remains were found.

f. Cro-Magnons founded our culture from about 35,000 to 8,000 B.C., as they shaped sophisticated tools, tailored clothing out of animal hides, passed on rituals and artifacts associated with life and death, painted, and sculpted (Figure 36.21).

g. Similar upper Paleolithic cultures existed with the Cro-Magnons, and they all had begun to settle into permanent communities as glaciers retreated, the earth warmed, and neothermal conditions came to exist.

h. As ecosystems changed, some people became adapted to different hunting, fishing, and gathering methods, while others invented a technique for obtaining food that would change the face of the earth: agriculture.

a. Traces of agricultural communities dating from about 8000 B.C. have been found in Asia, India, and the Middle East.

b. These first agricultural communities are defined as Neolithic (New Stone Age).

c. Between 10,000 and 20,000 years ago, farming techniques spread rapidly.

d. A dependable food supply made towns and cities possible and also led to a rapid population increase that has, since then, continued to be closely correlated with advances in agriculture.

e. The ability to smelt metal ores and fashion tools also improved the efficiency of agricultural techniques.