Chapter 21

Copyright © 2005 Brooks/Cole — Thomson Learning

Biology, Seventh Edition Solomon • Berg • Martin

Chapter 21

The Evolution of The Evolution of PrimatesPrimates


Biology, Seventh Edition CHAPTER 21 The Evolution of Primates

• Mammals• Endothermic

• Body hair

• Feed young with milk from mammary glands

• Most are viviparous



• Placental mammals• Placenta exchanges materials

between mother and fetus

• Newborns are more developed than marsupials



• Primates• Five grasping digits

• Opposable thumb or toe

• Long, freely moving limbs

• Eyes in front of the head

• Relatively large brain



Primate hands and feet



• Suborder Prosimii• Lemurs

• Suborder Tarsiiformes• Tarsiers

• Suborder Anthropoidae• Monkeys, apes, humans



Primate evolution



• Anthropoids• Old and new world monkeys• Apes and humans

• Hominoids• Apes

–Gibbons–Orangutans–Gorillas–Chimpanzees

• Humans



New world monkey Old world monkey



• Hominids• Humans

• Extinct human ancestors



• Differences between ape and human skeletons• Human adaptations for bipedal

life on the ground–Complex curvature of the spine

–Shorter, broader pelvis

–Foramen magnum at base of skull

–First toe aligned with other toes



Human and gorilla skeletons



Human and gorilla heads



• Sahelanthropus tchadensis• 6-7 mya

• May be the earliest known hominid

• Discovered in 2002



• Australopithecines• Bipedal

• Ardipithecus ramidus

• Australopithecus anamensis

• Australopithecus afarensis

• Australopithecus africanus



An interpretation of hominid evolution



• Homo habilis• Appeared 2.3 mya

• Human features not found in australopithecines

• Slightly larger brain

• Stone tools



• Homo erectus• Appeared 1.7 mya in Africa

• Larger brain than Homo habilis

• More sophisticated tools

• Maybe clothing, fires, shelters



Homo erectus skull



• Archaic Homo sapiens• Appeared 800,000 years ago

• Overlapped Homo erectus populations in Africa, Asia, and Europe and later Neandertals



• Neandertals• Appeared 230,000 years ago

• Short, sturdy builds

• receding chin and forehead

• Heavy supraorbital ridge

• Larger front teeth

• May be a separate species



• Homo sapiens• Appeared 100,000 years ago in

anatomically modern form• Lacked heavy brow ridge• Prominent chin• Complex weapons and tools• European Homo sapiens known

as Cro-Magnons



• Out-of-Africa hypothesis• H. sapiens evolved from African

H. erectus 200,000 to 100,000 ya

• Migrated to Europe and Asia

• Displaced more primitive humans



• Multiregional hypothesis• Modern humans evolved from

separate populations in Africa, Asia, and Europe ~2 mya

• Populations evolved separately but also interbred

• One species with regional variations that still exist



• Molecular anthropology• Comparison of biological

materials from modern populations

• Mitochondrial DNA

• Generally supports the Out-of-Africa hypothesis



• Cultural evolution• Transmission of knowledge

across generations• Enabled by large brain size• Agriculture• Industry• Rapidly expanding population

had degraded the environment

Chapter 21

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