Human evolution

Definition..

"Hominid" refers to members of the human family, Hominidae, which consist of all species from the point where the human line splits from apes towards present day humans.

Habitual bipedal locomotion (movement on two legs), an upright position, and a large brain that has lead to: tool use, language, and culture characterize hominids.

HOMINIDS

Human evolutionHistoryImportant stages in human evolutionTheories of human evolutionHuman CharacteristicsAre we still evolving?

1859 - Darwin publishes The Origin of Species1871- Darwin predicts that ancestors of humans would be found in Africa

HISTORY

Up till 1930sHumanity evolved in Europe

1950s--1960sMany significant fossils discovered

ABCDABCD

Bush modelLinear model

1970s presentmore fossils molecular techniquestree model of human evolution

Current Controversy

6-7 m y old fossil

Earliest bipedal hominid?

Sahelanthropus tchadensis

Important stages in human evolution3.2 million years ago3 million years ago2 million years ago1 million years ago200, 000 years ago150, 000 years ago

"Hominid" refers to members of the human family, Hominidae, which consist of all species from the point where the human line splits from apes towards present day humans.

Habitual bipedal locomotion (movement on two legs), an upright position, and a large brain that has lead to: tool use, language, and culture characterize hominids.

3.2 mya: The southern ape of afarFossil: Lucy (discovered 1974, Ethiopia)Australopithecus afarensis

Male

Fossil of LucyFemale

Australopithecus afarensisHabitat: savannah and woodland

Food: leaves, fruit, seeds, nuts, termites and eggs, grasses (?)

Physical characteristics: low forehead, flat nose, no chinsmall brainlong dangly arms, short legsfacultative bipedal (upright on ground but could dangle from branches)sexually dimorphic

Paranthropus boisei Homo habilis

3 mya: Paranthropus boiseiHabitat: open terrain

Food: nuts, roots and tubers

Physical characteristics: enormous jaw with chewing muscles, large back teeth, small front teethspecialized as vegetarians

Not direct human ancestors

3 mya: Homo habilis-the handy manHabitat: open terrainFood: Scavenged for meatPhysical characteristics: small jaw and teeth shorter armsincrease in brain size (because of carnivorous diet and mode of feeding)capable of speech

Oldowan Tools Made tools

Human migration1.9 mya humans began to leave Africa to other continents

Homo ergaster

2 mya: Homo ergasterHabitat: dry -hot habitat

Food: scavenger for meat

Physical characteristics: Tall with long limbsSmooth and dark skin Temperature regulation through sweatingNarrow pelvis (lead to narrow birth canal)Mothers needed support of partner and group to raise babies

Acheulean bifaces

Homo erectus

brain, almost human size stocky, human-like body (larger than Homo habilis) Java, China, and Africa use of fire increased but infrequent group hunting language crude shelters and some migration to colder areas used toolsHomo erectus

Homo heidelbergensis

1mya: Homo heidelbergensisFood: hunted for meat

Physical characteristics: Large brain Tall Direct ancestors of Homo sapiens

Boxgrove tools H.heidelbergensis made Hand axes, wooden spears etc.

200,000 ya: Homo neanderthalensismalefemale

200,000 ya: Neanderthal manHabitat: cold Food: hunted for meatPhysical characteristics: Large face with massive ridgesNo chinShort stocky body (conserve heat)Muscular LanguageSocial relationships important

What happened to the Neanderthals?Extinct 28, 000 yaCompetition from Homo sapiens?

120, 000 ya Physical characteristics: Eyebrow ridge small or absentProminent chinTools --antler, bone, stoneClothing, jewelry, artwork, musical instruments

Homo sapiens

Theories of human evolutionHumans evolved in sub-Saharan Africa and spread from thereorHumans evolved independently in several places around the globe

Out of Africa hypothesisHomo sapiens evolved in a single speciation event in Africa ~ 250, 000 ya

Migrated to other regions, replaced Homo erectus

Multi-regional hypothesisLocal populations of Homo erectus evolved into Homo sapiens

Mixed genes

Retained local characteristics

Support for multi-regional hypothesis

No break in culture in S.E Asia

Can explain the occurrence of regional characters

RacesOriginal skin color- black

Divergence from original black color to many different colors

How different are the races?No genetic discontinuities between racesGenetic differences between races only 10% of genetic diversity among humansNo evidence for major biological differences

Support for out of Africa hypothesis1. Level of diversity in maternally inherited mitochondrial DNA of humans from around the world highest among Africans

2. Based on genetic diversity all non-Africans descended from a small band of humans that left Africa ~ 100, 000 ya

Support for out of Africa hypothesis

3. The Y-chromosome too shows no sign of any non-African DNA

Support for out of Africa hypothesis

Australia --- ~60,000 yaEurope --- ~70,000 yaNear East --- ~90,000 yaAfrica --- ~130, 000 yaHuman migration

Who were the first Americans?13,000 yaCrossed Bering Strait

Human characteristicsBipedal gait Big brainTool makingSocial relationshipsArt Culture

BipedalismWhen? Before AustralopithecinesAdvantages: Freed hands to carry objects See predators better in grasslandsAccess to foods not previously availableCarry childrenProtection from sun in grasslands

Evolution of bipedalismCarrying objectsSee predatorsAquatic environment (?)

Evolution of big brainMeat eating from Homo habilis onwardsDid not require large intestinesEnergy freed up for other organs including brainorCooked tuber eating in Homo erectusHunter-gatherers rely less on meat than tubersReliance on scavenged meat is difficult.

Tool makingHomo habilis onwardsTool-making was considered a human traitDiscovery of tool-making in chimpanzeesTool making in Australopithecines?

Homo sapiens survived extinction in late Pleistocenebottlenecks (drastic reduction in population size )cultural explosionSocieties became co-operative (troop-to-tribe transition)Social relationships, art, and culture

Are we still evolving?

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