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Human Evolution Mader: Biology 8th Ed.
Outline • Evolution of Primates • Mobile Limbs • Binocular Vision • Evolution of Hominids • Early Homo • Modern Humans • Human Variation Mader: Biology 8th Ed.
Evolution of Primates • The evolution of primates is characterized by trends towards mobile limbs, grasping hands, a flattened face, binocular vision, a large, complex brain, and a reduced reproductive rate. Mader: Biology 8th Ed.
Mobile Limbs • Most primates have flat nails as well as sensitive pads on the undersides of fingers and toes. • Many also have both an opposable big toe and thumb. • Mobile limbs and clawless opposable digits allow primates to freely grasp and release tree limbs. Mader: Biology 8th Ed.
Primate Hands Mader: Biology 8th Ed.
Binocular Vision • Stereoscopic vision and resultant depth perception allows primates to make accurate judgments about distance and position of adjoining tree limbs. Mader: Biology 8th Ed.
Primate Characteristics • Opposable thumb • Nails instead of claws. • Single births • Binocular vision • Expanded, complex brain. • Emphasis on learned behavior. Mader: Biology 8th Ed.
Evolution of Primates • Prosimians were the first type of primate to diverge from the human line. • Surviving anthropoids are classified into three superfamilies. • New World monkeys • Old World monkeys • Hominoids Mader: Biology 8th Ed.
Hominoid Evolution • Proconsul is believed ancestral to hominids. Mader: Biology 8th Ed.
Evolution of Hominids • Phylogenetic tree indicates humans are most closely related to African apes. • Last common ancestor appears to have lived about 7 mya. • Genetic changes used as a molecular clock to measure relatedness of different groups. Mader: Biology 8th Ed.
Hominids • To be a hominid, a fossil must have an anatomy suitable for standing erect and walking on two feet. • Bipedalism • Human anatomy differs from that of an ape largely because humans are bipedal while apes are quadrupedal. Mader: Biology 8th Ed.
Australopithecines • It is possible that one of the australopithecines that evolved and diversified in Africa 4 mya is a direct ancestor of humans. • Southern Africa • Australopithecus africanus • Eastern Africa • Australopithecus afarensis Mader: Biology 8th Ed.
Evolution of Early Homo • Homo habilis, dated between 2.0 an 1.9 mya, may be ancestral to modern humans. • Skulls suggest portions of the brain associated with speech were enlarged. • Ability to speak may have led to hunting cooperatively and the advent of culture. Mader: Biology 8th Ed.
Human Evolution Mader: Biology 8th Ed.
Homo erectus • Homo erectus and like fossils are found in Africa, Asia, and Europe and are dated between 1.9 and 0.3 mya. • Larger brain and flatter face than Homo habilis. • Much taller than previous hominids. • Believed to have first appeared in Africa and then migrated into Asia and Europe. • First hominid to use fire. Mader: Biology 8th Ed.
Evolution of Modern Humans • Most researchers believe Homo sapiens evolved from Homo erectus. • Multiregional Continuity Hypothesis • Similar evolution occurred in many different places. • Out-of-Africa Hypothesis • H. sapiens evolved from H. erectus only in Africa, and thereafter migrated to Europe. Mader: Biology 8th Ed.
Evolution of Modern Humans Mader: Biology 8th Ed.
Neanderthals • Neanderthal (H. neanderthalensis) skeletons were first discovered in Germany’s Neander Valley. • Skeletons date back 200,000 years. • Massive brow ridges with protruding nose, jaws, and teeth. • Heavily muscled. • Culturally advanced. • Manufactured variety of tools. Mader: Biology 8th Ed.
Cro-Magnons • Oldest fossils to be designated H. sapiens. • Modern humans who entered Asia and Europe from Africa 100,000 years ago. • Made advanced stone tools. • Accomplished hunters. • Hunted cooperatively. • First to have language. Mader: Biology 8th Ed.
Human Variation • It has been hypothesized that human variations evolved as adaptations to local environmental conditions. • Bergmann’s Rule - Animals in colder regions of their range have a bulkier body build. • Allen’s Rule - Animals in colder regions of their range have shorter limbs, digits, and ears. Mader: Biology 8th Ed.
Human Variation • Comparative study of mitochondrial DNA shows differences among human populations are consistent with their having a common ancestor no more than a million years ago. Mader: Biology 8th Ed.
Review • Evolution of Primates • Mobile Limbs • Binocular Vision • Evolution of Hominids • Early Homo • Modern Humans • Human Variation Mader: Biology 8th Ed.