Chapter 17: Human Evolution

Chapter 17: Human Evolution

Classification Hierarchy Kingdom Phylum Class Order Family Genus Species Animal Chordate Mammal Primates Hominids Homo 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:

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. Mobile 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)

Lucy A reconstruction of Lucy s skeleton Lucy is ~ 3.5-millionyears-old Australopithecus afarensis adaptations in Lucy s hip, leg and foot allowed a fully bipedal means of locomotion

Hominid Footprints 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

Re-creation of a Pliocene landscape showing members of A. Afarensis gathering and eating various fruits and seeds Landscape with A. 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. 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 Homo Erectus Neanderthal Homo Sapiens

Cultural Evolution 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

Homo Sapiens 100,000 yrs ago Art: Cave Paintings, Venuses Oldest paintings: Chauvet (32,000 yrs old) Peche Merle (15,000 yrs old) Lascaux (17,000 yrs old)