mader: biology 8 th ed. human evolution chapter 32

Mader: Biology 8th Ed.

Human Evolution

Chapter 32


Outline

• Evolution of Primates– Mobile Limbs– Binocular Vision

• Evolution of Hominids– Early Homo– Modern Humans

• Human Variation


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.


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.


Primate Hands


Binocular Vision

• Stereoscopic vision and resultant depth perception allows primates to make accurate judgments about distance and position of adjoining tree limbs.


Primate Characteristics

• Opposable thumb• Nails instead of claws.• Single births• Binocular vision• Expanded, complex brain.• Emphasis on learned behavior.


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


Hominoid Evolution

• Proconsul is believed ancestral to hominids.


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.


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.


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


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.


Human Evolution


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.


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 HypothesisH. sapiens evolved from H. erectus only

in Africa, and thereafter migrated to Europe.


Evolution of Modern Humans


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.


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.


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.


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.


Review

• Evolution of Primates– Mobile Limbs– Binocular Vision

• Evolution of Hominids– Early Homo– Modern Humans

• Human Variation

mader: biology 8 th ed. human evolution chapter 32

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