Week 4 - Human Evolution

when did primates evolve?

Primates evolved with the extinction of dinosaurs about 65 mya

what makes humans human?

• bipedal locomotion → evolved as an efficient way for apes to travel on the ground

  • quadrupeds are faster but humans are good LONG DISTANCE

  • good way to keep cool in open country with less solar radiation and more wind

  • leaves hand free to carry things

• derived dentition and jaw musculature

• larger brains in relation to body

• slower development

• language and culture

when did bipedal locomotion and derived dentition and jaw musculature evolve

begin to appear 7-6 mya, australopithecines (4-2 mya) showed these traits

when did larger brains in relation to our body size

begin to appear in the genus homo around 2 Mya

when did language and culture begin to form

at least by 200 thousand years ago

where and when were australopithcines

pliocene epoch (5.3-2.6 ma)

who was lucy

An australopithecus afarensis - a bipedal hominid from 3.5 mya - found in East Africa

what are the differences between australopithecines and modern human

australopithecines were also fully bipedal and sexually dimorphic but were much smaller than humans

• australopithecines had brains that were about 400mL (similar to chimps), humans brains are around 1450 cubic centimeters

when did the genus homo appear - what changed

homo erectus → around 2 mya, climate got colder in the Pleistocene (1.6ma- 12ma), led to isolations of populations and adaptions to changing environments

• brain size also doubled from 400cc in australopithecine to 8— in hoo ergaster/erectus

how did homo ergaster compare to modern humans?

• developed slower than early hominins, but faster than modern humans

• shorter childhood than modern humans with less learning

• tools became more complex → achulean tools (mode 2, 1.6MA) - hand axes, cleavers and picks

• fire invented

what were the first (mode 1) tools like

Oldowan stone tools, used by australopithecines or early homo - unchanged for a mil years 2.5-1.7ma

what was the step after homo erectus? what tools did they use?

Homo heidelbergensis → much larger brain 1200 cc, used mode 3 stone tools

what was the step after Homo heidelbergensis?

Homo neanderthalis (600,000 → 33,000 years ago), discovered in the Neander Valley in germany.

• archaic humans

• adapted to colder climate, shorter & stockier than us

• larger brains 1520 cc compared to our 1450 cc

were neatherthals similar to us?

• Hyoid bone as possible evidence for language

• made complex tools and hunted large prey

• buried their dead, perhaps without ritual

• cared for their sick

• few lived past 40y/o, skeletons show evidence of arthritis, gum disease, fractured skills, lesions, stab wounds

who evolved in Europe & Africa

Neanderthals evolved in Europe, Hominins in Africa were becoming Homo sapiens 190-90,000 years ago

how were Homo sapiens similar to us

Anatomically modern (100-300Ka)

• modern behaviour in paleolithic era 40-50Ka e.g. art

• more complex (mode 4) tools

• built shelters

• domesticated dogs

• ritual burials

• arts & crafts

• no gap between emergence of modern humans and modern behaviour

when were homo sapiens the only hominin left? why?

30ka → neanderthals were likely wiped out by competition rather than direct conflict or disease

• neaderthals interbred with early h. sapiens, about 1.5-2.6% of DNA in non-Africans due to interbreeding with Neanderthals - some of the genes associated with higher cholesterol, more belly far, sunburn, arthritis and schizophrenia

who are the homo floresiensis & denisovans

• homo floresiensis were still living on the island of Flores, Indonesia until 14ka - shares many features with Homo erectus, uses mode 4 tools

• Denisovans, discovered in Siberia 41ka

outline the Piltdown Man Hoax of 1912

• tried to make it seem like humans evolved in England → exposed as a hoax in 1953

• Dawson forged it using medieval skull, orangutan jaw, chimp teeth

outline the multiregional hypothesis

Humans evolved about 2ma from homo erectus - different populations evolved in Africa, europe, asia, and Australasia with gene flow between them

outline the singe origin ‘out of Africa’ hypothesis

more widely accepted → modern humans evolved around 200 ka, 1st wave of migration to europe from northern africa around 130 ka and the second wave from southern africa to the whole world

what are ongoing debates in this field?

• is Homo heidelbergensis a distinct species?

• are h. ergaster and h. erectus the same species

• individual variation may be misclassified as different species

what does modern human DNA look like

• humans have little genetic variation compared to great apes

• during the course of migration, humans would have gone through population bottlenecks, decreasing genetic diversity

differences between human and chimp hunters

• chimps use tools as did early homonins, stone tools first appeared 2.5Ma

• human foragers collect, extract and hunt foods

• humans rely more on hard-to-acquire foods than apes

expensive tissue hypothesis

big brain is an expensive thing to have in your body, but gives you the resources to get more food

• meat, especially cooked requires smaller guts allowing more energy for larger brains

outline the hunting sexual division of labour

women mainly forage, men mainly hunt → only possible if men and women share

• Men usually bit bigger and stronger ( but this is for fighting other males)

• BUT - women do hunt (evidence during the stone age and possibly much earlier), females in wolves etc.

  • Tend not to because of the burden of childhood

  • may have led to reduced dimorphism

how is food sharing different in chimps and humans

• Chimps mostly eat what they collect, mothers share with infants, males share small amounts of meat

• Food sharing is extensive in humans