Human evolution Chapter 34

Humans???

Archonta 65 mya Small arboreal (tree-dwelling) mammals Large eyes Insect eating Nocturnal Gave rise to bats, tree shrews & primates

Primates 1. Grasping fingers & toes Opposable thumb 2. Binocular vision Eyes are shifted in front 2 fields of vision Helps with depth perception

Primates Initially insect eating Teeth adapted to eat plants Fewer number of teeth Snout length began to get smaller

Primates Split into 2 groups 40 mya 1. Prosimians “before monkey” lemurs, lorises and tarsiers Common in NA, Europe, Asia & Africa Increased visual acuity Fruit, leaves & flowers

Lemurs

Lorises

Tarsiers

Primates 2. Anthropoids Monkeys, apes, humans Diurnal: active during the day Feeding fruits & leaves Color vision evolved-daytime foraging Expanded cortex for improved senses

Anthropoids Live in groups Complex social interactions Care for young for extended time Nurtures brain development

Aye-Aye

Spider monkey

Anthropoids New World monkeys (Americas) 30 mya migrated to SA Isolated Arboreal (tree-dwelling) Flat spreading noses Prehensile tails Helps hanging in trees

Squirrel monkey

Capuchins

Anthropoids Old world monkeys Ground dwelling Some arboreal Nostrils come together Noses point down Toughened pads of skin to sit upon No prehensile tails

Old world monkeys Baboons, mandrills, macaque

Mandrill

Baboon

Pig-tail macaque

Anthropoids 25 mya Hominoids (human line) Branched from old world monkeys 1. Hominins (humans) 2. Ape group Gibbons, Orangutans, Gorilla, and Chimpanzees

Hominoids

Chimpanzee

Gibbon

Gorilla

Orangutans

Apes Larger brain than monkeys Lack tails Long arms & short legs Most larger than monkeys Except Gibbon Gibbons & orangutans are arboreal

Apes Gorillas & chimpanzees highly social Behavior more adaptable Spread over Africa & Asia None in NA & SA

Gorilla

Apes Chimpanzee split from common ancestor about 6 mya Genes of human & chimpanzees similar Shares 98.6% of DNA Human Hgb only one aa different

Chimpanzee

Compare Apes to hominins Common ancestor arboreal climber Hominins bipedal Walking upright Apes are knuckle walkers Support weight on fingers

Compare Apes to hominins Vertebral column more curved Spinal cord exits at bottom of the skull Rather than the back Pelvis is more bowl shaped Pelvis bones curve forward to support more weight Legs are longer than arms support more weight

Compare Apes to hominins Larger brain Capable of language Manufacture & use tools Reduced jawbones & jaw muscles Shorter digestive tract

Primates Prosimians Anthropoids 1. New world monkeys 2. Old world monkeys 3. Hominoids Apes (Gibbons, Orangutans, Gorilla, Chimpanzee) Hominins

Paleoanthropology Study of human evolution Chimpanzees & Hominins 2 divergent branches of hominoid tree Homo sapiens Multi branched bush

Hominins Upright position came first Enlarged brain coming second Mosaic evolution: Different features evolved at different rates

Hominins Why upright? Tools found until 2.5 mya Faster/less energy Pick fruits/carry food See over tall grass

Hominins 10 mya climate became drier/cooler Savannas & grasslands More time walking in open habitats Less time in trees

Hominins Brain size tripled cm 3 to about 1,300 cm 3 in modern humans Reduced size difference between sexes Gorilla & orangutan males 2X heavier than females Humans average male is 1.2X heavier

Hominins Two major groups of Hominins Genus Homo (3-7 species) Genus Australopithecus Latin australo, meaning “southern” Greek pithecus meaning “ape” Approximately 7 species Older genus-smaller brains

Australopithecus A. africanus Skull 2.8 million years old Walked fully erect Human-like hands & teeth Brain 1/3 size of a modern human

Australopithecus “Lucy” Afar region of Ethiopia A.afarensis 40% complete skeleton 3.24 mya

Homo 1960 East Africa Homo habilis- “handy man” Fossils of earliest genus Homo. 2.5 to 1.6 mya Found with tools

Homo H. ergaster “workman” Fossils date 1.9 to 1.5 mya Larger brain (900cm 3 ) Longer slender legs Hip joints-walking Fingers short & straight Smaller teeth----cooked food Early ancestor to later species of Homo

Homo ergaster

Homo erectus First hominins to migrate out of Africa Colonizing Asia & Europe “java man” or “Peking man” Lived 1.8 million to 500,000 years ago Larger than Homo habilis-1.5 meters Larger brain (1000 cm 3 ) Sexual dimorphism similar to modern man

Homo erectus Social species Lived in tribes of people Dwelling in caves Hunted large animals Used flint for fires Lived longer than any other species

Homo neanderthalensis Neanderthals Lived in Europe 200,000 to 40,000 years ago Thick boned, heavy hominins Prominent brow Brain size of humans Extinct 30,000 years ago

Homo sapiens Originated in Africa-DNA evidence Older species (H.ergaster or H.erectus) gave rise to H. sapiens Oldest fossils dated 195,000 to 160,000 years in Ethiopia Oldest fossils outside of Africa is 40,000 years old

Homo sapiens Humans spread to NA 13,000 years Only surviving hominins Increasing brain size Use tools Symbolic language Shape concepts out of experience Transmit experience from one generation to another