Human evolution

Chapter 34

Humans???

Archonta

65 myaSmall arboreal (tree-dwelling) mammals Large eyesInsect eatingNocturnal Gave rise to bats, tree shrews & primates

Primates

1. Grasping fingers & toesOpposable thumb2. Binocular visionEyes are shifted in front 2 fields of vision help with depth perception

Primates

Initially insect eatingTeeth adapted to eat plantsFewer number of teethSnout length began to get smaller

Primates

Split into 2 groups 40 million years ago1. Prosimians “before monkey”Common in NA, Europe, Asia & Africalemurs, lorises and tarsiersIncreased visual acuityFruit, leaves & flowers

Primates

Lemurs & lorisesMadagascar, Africa, southern AsiaTarsiersSmall nocturnal tree-dwellers Southeast Asia

Lemurs

Lorises

Tarsiers

Primates

2. AnthropoidsMonkeys, apes, humansDiurnal: active during the dayFeeding fruits & leavesColor vision evolved-daytime foragingExpanded cortex for improved senses

Aye-Aye

Spider monkey

Anthropoids

Oldest known anthropoid fossilsAbout 45 mya Supports Tarsiers are prosimians Most closely related to anthropoids

Anthropoids

Live in groupsComplex social interactionsCare for young for extended timeNurturing development of brain

Anthropoids

New World monkeys (Americas)30 mya migrated to South AmericaIsolatedArboreal (tree-dwelling)Flat spreading nosesPrehensile tailsHelps hanging in trees

Squirrel monkey

Capuchins

Anthropoids

Old world monkeysGround dwellingSome arborealNostrils come togetherNoses point downToughened pads of skin to sit uponNo prehensile tails

Old world monkeys

Baboons, mandrills, macaque

Mandrill

Baboon

Pig-tail macaque

Anthropoids

25 mya Hominoids (human line)Branched from old world monkeys1. Hominins (humans)2. Ape groupGibbons, Orangutans, Gorilla, and Chimpanzees

Hominoids

Chimpanzee

Gibbon

Gorilla

Orangutans

Apes

Larger brain than monkeysLack tailsLong arms & short legsMost larger than monkeysExcept GibbonGibbons & orangutans are arboreal

Apes

Gorillas & chimpanzees highly socialBehavior more adaptableSpread over Africa & Asia None in NA & SA

Gorilla

Apes

Chimpanzee split from common ancestor about 6 myaGenes of human & chimpanzees similarShares 98.6% of DNAHuman Hgb only one aa different

Chimpanzee

Compare Apes to hominins

Common ancestor arboreal climberHominins bipedalWalking uprightApes are knuckle walkersSupport weight on fingers

Compare Apes to hominins

Vertebral column more curvedSpinal cord exits at bottom of the skull Rather than the backPelvis is more bowl shaped Pelvis bones curve forward to support more weightLegs are longer than armssupport more weight

Compare Apes to hominins

Larger brainCapable of languageManufacture & use toolsReduced jawbones & jaw musclesShorter digestive tract

Primates

ProsimiansAnthropoids1. New world monkeys2. Old world monkeys3. Hominoids

Apes (Gibbons, Orangutans, Gorilla, Chimpanzee)Hominins

Paleoanthropology

Study of human evolutionMisconceptions1. Ancestors were chimpanzees Chimpanzees & Hominins 2 divergent branches of hominoid tree

Hominins

2. Lineage straight line to Homo sapiensMulti branched bush

Hominins

3. Upright posture & enlarged brain came togetherUpright position came first Enlarged brain coming secondMosaic evolution:Different features evolved at different rates

Hominins

Why upright?Tools found until 2.5 myaFaster/less energyPick fruits/carry foodSee over tall grass

Hominins

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

Hominins

Brain size tripled 400-450 cm3 to about 1,300 cm3 in modern humansReduced size difference between sexes Gorilla & orangutan males 2X heavier than femalesHumans average male is 1.2X heavier

Hominins

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

Australopithecus

1924 first hominins fossil foundSouth Africa Skull 2.8 million years oldA. africanusWalked fully erectHuman-like hands & teethBrain 1/3 size of a modern human

Australopithecus

“Lucy”1974-fossil discoveredAfar region of EthiopiaA.afarensis 40% complete skeleton3.24 mya

Australopithecus

Pelvis shape-femaleLeg bones-uprightTeeth-homininsHead shaped like an apeStood approximately 1 meter tallBrain no larger than a chimpanzee

Australopithecus

A. robustus Second stockier skeleton discoveredMassive teeth & jawA. Boisei (after Charles Boise)Even more stocky- 2 million yrs old

Older hominins

2002Earliest homininsDated 6-7 million years old

Older hominins

1994 EthiopiaDiscovered complete fossil skeleton4.4 myaMore ape like BipedalNew genus Ardipithecus ramidus (ardi means “ground”, ramid means “root”)

Homo

1960East AfricaHomo habilis- “handy man” Fossils of earliest genus Homo. 2.5 to 1.6 myaFound with tools

Homo

H. ergaster “workman”Fossils date 1.9 to 1.5 myaLarger brain (900cm3)Longer slender legsHip joints-walkingFingers short & straight Early ancestor to later species of Homo

Homo

H. ergaster More sophisticated toolsSmaller teethSuggested cooked foods Fossil of adolescence male 1.5 meters tall, weighed 47 kilograms

Homo ergaster

Homo erectus

First hominins to migrate out of AfricaColonizing Asia & EuropeLived 1.8 million to 500,000 years agoLarger than Homo habilis-1.5 metersLarger brain (1000 cm3)Sexual dimorphism similar to modern man

Homo erectus

Social speciesLived in tribes of 20-50 peopleDwelling in cavesHunted large animalsUsed flint for firesLived longer than any other species

Homo erectus

“Java Man” & “Peking Man”Fossils found in ChinaH. erectus extinct 200,000 years ago

Homo neanderthalensis

Neanderthals1856 in GermanyFossil dating 40,000 years oldLived in Europe 200,000 to 40,000 years ago Thick boned, heavy homininsProminent browBrain size of humansExtinct 30,000 years ago

Homo sapiens

Originated in Africa-DNA evidenceOlder species (H.ergaster or H.erectus) gave rise to H. sapiensOldest fossils dated 195,000 to 160,000 years in EthiopiaOldest fossils outside of Africa is 40,000 years old

Homo sapiens

Humans spread to NA 13,000 years By 10,000 there were 5 million spread through the world.

Homo sapiens

Only surviving homininsIncreasing brain sizeUse toolsSymbolic languageShape concepts out of experienceTransmit experience from one generation to anotherChange environment