7 C H A P T E R THE PRIMATES 7-2

THE PRIMATES Our Place Among Primates Homologies and Analogies Primate Tendencies Prosimians Monkeys Apes Behavioral Ecology and Fitness Primate Evolution Chronology Early Primates Miocene Hominoids 3

THE PRIMATES How and why are monkeys and apes similar to humans? When, where, and how did the first primates, monkeys, apes, and hominids evolve? How did diversity among Miocene proto-apes figure in hominid origins?

PRIMATOLOGY Primatology: the study of nonhuman primates—fossils and living apes, monkeys, and prosimians—including their behavior and social life Terrestrial monkeys and apes: primates that live on the ground rather than in trees Great apes, specifically chimpanzees and gorillas Most closely related to us

OUR PLACE AMONG PRIMATES Similarities between humans and apes evident in anatomy, brain structure, genetics, and biochemistry Taxonomy: assignment of organisms to categories Phylogeny: genetic relatedness based on common ancestry Hominoidea (hominoids): a superfamily containing humans and apes

OUR PLACE AMONG PRIMATES Homologies: similarities that organisms share because of a common ancestry Mammals Primates share structural and biochemical homologies that distinguish them from other mammals Resemblances inherited from common early primate ancestors

Figure 7.1: The Principal Classificatory Units of Zoological Taxonomy 8

Table 7.1: The Place of Humans (Homo sapiens) in Zoological Taxonomy 9

Table 7.2: Primate Taxonomy 10

HOMOLOGIES AND ANALOGIES Extensive biochemical homologies between apes and humans confer a common ancestry Analogies: similar traits that arise if species experience similar selective forces and adapt to them in similar ways Convergent evolution: process by which analogies are produced

HOMOLOGIES AND ANALOGIES Hominid: the zoological family that includes fossils and living humans, chimpanzees, gorillas, and their common ancestors Tribe hominini describes all human species that have ever existed, excluding chimps and gorillas Scientists today use the word hominin to describe the zoological family of humans but not chimps and gorillas

Figure 7.2: Primate Family Tree 13

PRIMATE TENDENCIES Primates have varied because of adapting to diverse ecological niches Modern primates share homologies reflecting a common arboreal (living in trees) heritage

PRIMATE TENDENCIES Many trends in primate evolution best exemplified by anthropoids: monkeys, apes, and humans constituting the suborder Anthropoidea Prosimians: primate suborder that includes lemurs, lorises, and tarsiers

PRIMATE TENDENCIES Grasping: opposable thumbs can touch all other fingers Adaptation of hominins to bipedal locomotion: two-footed, upright locomotion Shift from smell to sight Hand, rather than nose, is main touch organ Increased brain complexity Parental investment in single offspring Sociality

PROSIMIANS Primate order has two suborders: Anthropoids Early history of primates limited to prosimian-like animals known through the fossil record The first anthropoids appeared more than 40 million years ago

PROSIMIANS Some prosimians managed to survive in Africa and Asia because they adapted to nocturnal life They do not compete with anthropoids, which are active during the day Lemurs Tarsiers Lorises

MONKEYS All anthropoids share resemblances that can be considered trends in primate evolution Anthropoid suborder has two infraorders: Platyrrhines: flat-nosed, New World monkeys Catarrhines: sharp-nosed, Old World monkeys, hominoids

MONKEYS All New World monkeys, and many Old World ones, are arboreal Monkeys move differently from apes and humans Their arms and legs move parallel to each other Most monkeys have tails

NEW WORLD MONKEYS Live in the forests of Central and South America Have prehensile, or grasping, tails With one exception, all monkeys, apes, and humans are diurnal

Figure 7.3: Nostril Structure of Catarrhines and Platyrrhines 22

OLD WORLD MONKEYS Terrestrial and arboreal Significant distinctions exist between arboreal and terrestrial Old World monkeys Size: arboreal monkeys smaller than terrestrial ones Sexual dimorphism: marked differences in male and female anatomy and temperament Terrestrial males significantly larger and fiercer than terrestrial females, but little or no such differentiation exists among arboreal monkeys

APES Old World monkeys have separate superfamily (Cercopithecoidea) Humans and apes make up hominoid superfamily (Hominoidea) Subdivided into families: Great apes: orangutans, gorillas, chimpanzees Lesser (smaller) apes: gibbons, siamangs The third African ape: humans

APES Live in forest and woodlands Light and agile gibbons are completely arboreal Skilled brachiation: hand-over-hand movement through the trees Heavier gorillas, chimpanzees, and adult male orangutans spend considerable time on the ground Ape behavior and anatomy reveal past and present adaptation to arboreal life

GIBBONS Smallest of the apes Spend most of their time just below the forest canopy Use arms as balance when they occasionally walk erect Tend to live in primary groups composed of permanently bonded males and females and their preadolescent offspring

Figure 7.4: The Limb Ratio of the Arboreal Gibbon and Terrestrial Homo 27

ORANGUTANS Two existing species Marked sexual dimorphism Male is between chimps and gorillas in size Move between arboreal and terrestrial habitats Tend to be solitary Tightest social units: females and preadolescent young

GORILLAS Three subspecies: Western lowland Eastern lowland Mountain Full-grown male may be 400 pounds, 6 feet tall Marked sexual dimorphism Spend little time in trees Live in a troop of males and females with their offspring

CHIMPANZEES Two kinds of chimpanzee: Common (Pan troglodytes) Pygmy (Pan paniscus) Adult males weigh 100 to 200 pounds Less sexual dimorphism than gorillas Social organization relatively well known Chimps greet with gestures, facial expressions, and calls

BONOBOS Belong to species Pan paniscus Live in humid forests of Democratic Republic of Congo Adult males average 95 pounds Female-centered communities Peace loving Egalitarian Frequently use sex to avoid conflict within community

BEHAVIORAL ECOLOGY AND FITNESS Behavioral ecology: study of evolutionary basis for behavior Assumes genetic features of any species reflect a long history of differential reproductive success Individual fitness measured by number of direct descendants an individual has Inclusive fitness is measured by genes one shares with relatives

BEHAVIORAL ECOLOGY AND FITNESS Maternal care always makes sense in terms of the reproductive fitness theory, because females know that offspring are their own If male cannot be sure about an offspring’s paternity, it may make sense to invest in a sister’s offspring, because of shared genes

PRIMATE EVOLUTION Fossil record offers evidence for no more than 5 percent of extinct primates Discussions of primate and human evolution must be tentative

CHRONOLOGY Paleozoic (544–245 m.y.a.—million years ago) Era of ancient life—fish, amphibians, and primitive reptiles Mesozoic (245–65 m.y.a.) Era of middle life—reptiles, including dinosaurs Cenozoic (65 m.y.a.–present) Era of recent life—birds and mammals Each era is divided into periods, and the periods are divided into epochs

CHRONOLOGY Anthropologists concerned with Cenozoic era: Tertiary period: Paleocene Eocene Oligocene Miocene Pliocene Quaternary period: Pleistocene Holocene (or Recent)

Figure 7.5: Periods and Epochs of the Cenozoic Era 37

Figure 7.6: Placement of Continents at the End of the Mesozoic 38

EARLY PRIMATES During Cenozoic, most land masses had tropical or subtropical climates Arboreal theory: primates became primates by adapting to arboreal life Importance of sight over smell Development of depth perception facilitated leaping Grasping hands and feet

EARLY CENOZOIC PRIMATES The earliest primates most likely lived during the first part of the Cenozoic, the Paleocene (65–54 m.y.a.) Eocene (54–38 m.y.a.) was age of prosimians, with at least 60 different genera in two families

EARLY CENOZOIC PRIMATES Anthropoids branched off from prosimians during Eocene Eyes rotated forward Fully enclosed bony eye socket developed A dry nose is separated from an upper lip By end of the Eocene, many prosimian species extinct, reflecting competition from anthropoids

OLIGOCENE ANTHROPOIDS During the Oligocene (38–23 m.y.a.), anthropoids became most numerous primates Of the Fayum anthropoid fossils, one group is more primitive and perhaps ancestral to New World monkeys Another Fayum group seems ancestral to catarrhines—Old World monkeys, apes, and humans

MIOCENE HOMINOIDS Earliest hominoid fossils date to the Miocene epoch (23–5 m.y.a.) Hominoids—zoological superfamily that includes extinct and living apes and hominins—called proto-apes, but none are identical to or very similar to modern apes

PROCONSUL Proconsul: represents most abundant and successful anthropoids of early Miocene Teeth similar to those of living apes Skeleton below the neck more monkeylike Dentition suggests they ate fruits and leaves By middle Miocene, Proconsul replaced by Old World monkeys and apes

LATER MIOCENE APES Gigantopithecus Confined to Asia Persisted for millions of years, from Miocene until 400,000 years ago Largest ape that ever lived (1,200 pounds; 10 feet tall) Two species: one coexisted with H. erectus in China and Vietnam; another, much earlier (5 m.y.a.), lived in northern India

PIEROLAPITHECUS CATALAUNICUS Discovered in Spain May be last common ancestor of world’s living great apes Lived around 13 million years ago Well adapted for tree climbing and knuckle walking on the ground Probably a fruit eater