Chapter 17: Human Evolution

Classification Hierarchy

Kingdom Animal Phylum Chordate

Class Mammal Order Primates Family Hominids Genus Homo Species Sapiens

Important Vocabulary

_____________ •  Scientist who studies

fossil evidence of human evolution.

_____________ •  Group that includes

humans and their immediate ancestors.

Background

•  It is very rare to find a complete skeleton of a fossilized hominid. –  Scientists need to look at many different

things to try and piece together the puzzle of human evolution.

Background Cont’d

•  When hominid fossils are found, several important characteristics can help determine origin and lifestyle of the species.

–  __________________________ v Curvature of spine, position where spine

attaches to skull and shape of pelvis –  _____________

v Examine skull fragments –  _____________

v Wear and tear on fossilized teeth –  __________________________

v Fossils found in same area & environment found

Primate Characteristics

•  Hominids belong to the order of mammals known as ____________.

•  There are two large divisions of primates:

–  _______________: Marmosets, Monkeys, Apes (including humans)

–  _____________: Lemurs, Lorises and Tarsiers

•  Since most primates live in trees, many of their characteristics evolved as adaptations to life in trees.

Primate Characteristics

•  ALL primates share the following characteristics:

–  __________________________ –  flattened nails instead of claws –  __________________________ –  binocular vision (front-facing eyes allow for

depth perception) –  color vision (may have evolved since primates

are more active during the day than at night)

Anthropoids

•  Have all of the previous characteristics, plus these: •  a large, complex brain (for learned behavior) •  opposable thumbs (allows for precision use of

the hand) •  rotating shoulder joint •  similar dental formula: ___________________ ___________________________________

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 ________ _____________ allows primates to make accurate judgments about distance and position of adjoining tree limbs.

Where Humans Differ

•  We have all the previous characteristics, plus a few of our own:

–  _____________ à Ability to walk primarily on two legs

–  Cup-Shaped pelvis (supports internal organs while walking upright)

–  _____________ (allows for upright walking) –  Shorter toes that are aligned with each other –  Larger brain with extensive areas devoted to

_____________ –  Rounder jaw

Hominid Evolution •  Non-human primates are quadrupeds

–  Walk on four limbs •  Ancestors of first hominids were probably also

quadrupeds •  Fossil evidence shows that walking upright

apparently came before many of the other adaptations that make hominids unique

•  Important to remember: –  many hominid forms evolved, died out and left

no descendants –  species of hominids lived at the same time and

sometimes in the same area

Evolution of Primates

•  Prosimians were the first type of primate to diverge from the ancestral primate 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 6-8 million years ago (mya) v 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 v 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

v Australopithecus africanus –  Eastern Africa

v Australopithecus afarensis (Lucy)

•  A reconstruction of Lucy’s skeleton

•  Lucy is ~ 3.5-million-years-old –  Australopithecus

afarensis –  adaptations in Lucy’s hip,

leg and foot allowed a fully bipedal means of locomotion

Lucy

•  Preserved in volcanic ash in Tanzania

–  Discovered in 1978 –  Proved hominids

were bipedal walkers at least 3.5 million years ago

–  Most scientists think the footprints were made by A. afarensis, whose fossils are found nearby

Hominid Footprints

Landscape with A. afarensis

Re-creation of a Pliocene landscape showing members of A. Afarensis gathering and eating various fruits and seeds

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. v Ability to speak may have led to hunting

cooperatively and the advent of culture.

Human Evolution

•  A reconstruction of the skull of Homo erectus

–  a widely distributed species

–  whose remains have been found in Africa, Europe, India, China, and Indonesia

Skull of Homo erectus

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

v Similar evolution occurred in many different places.

–  Out-of-Africa Hypothesis v H. 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.

v Massive brow ridges with protruding nose, jaws, and teeth.

v Heavily muscled. v Culturally advanced.

Ø Manufactured variety of tools.

•  Reconstructed Neanderthal skull

•  characterized by prominent heavy

brow ridges and week chin

Burial Ceremony in a Cave

Neanderthals lived in caves and had ritual burials, such as this depiction from Shanidar Cave, Iraq

Neanderthals (190,000 – 27,000 yrs ago)

Flaked stones that fit in wood handles.

Buried their dead with spices and bedding.

Built sturdy huts.

Made flutes!

A flute formed from a femur & 4 remaining holes.

Cro-Magnons – Homo sapiens

•  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.

v Hunted cooperatively. –  First to have complex language?

Homo Floresiensis (hobbits)

- one meter high - lived in Flores 12,000 yrs ago - Upright posture - 380 cc cranial size (like a chimp)

The shapes & sizes of hominid heads can be seen to evolve with time.

Australopithecus vs. Modern

Australopithecus, 4-3 myrs ago Modern human

Chimpanzee

Cranial Comparisons

Neanderthal Homo Erectus Homo Sapiens

•  With the appearance of Cro-Magnons, –  human evolution has become almost

entirely cultural rather than biological

•  Humans have spread throughout the world –  by devising means to deal with a broad

range of environmental conditions

Cultural Evolution

Homo Sapiens 100,000 yrs ago

Art: Cave Paintings, Venuses

Lascaux (17,000 yrs old)

Oldest paintings: Chauvet (32,000 yrs old)

Peche Merle (15,000 yrs old)