Human evolution

Human evolution

1. what makes us human

   • Bipedal locomotion, derived dentition and raw musculature, larger brains in relation to body size, slower development, language and culture
     • Bipedal locomotion and derived dentition and jaw musculature began to appear about 7-6 million years ago (australopithecines show these trains 4-2 mill) - large brains kicks in around appearance of homo around 2 mill years ago - language and culture around 200 thousand years ago but not entirely sure
       • Why did bipedality evolve? efficient way for apes to travel on the ground - however, quadrupeds are faster, walking is a controlled fall - on the other hand, humans are the words bests long distance runners
         • good way to keep cool in open country - chimps and other apes live in forrest environments - but in move to savanna, it made sense to be able to move on open ground but it is hot - being bipedal beneficial for feeling less hot - leaves hands free to carry things too e.g tools - efficient for harvesting fruit
           • study looked at bipedal locomotion in chimps - found they walk quite differently, with their hips swinging more

2. Australopithecines

   • Pilocene epoch (5.3 to 2.6 mill years ago - phylogenetic relationship among hominids is unknown - most famous one is Lucy - 3.5 mill years ago in east Africa, paticularly Ethiopia, - they were fully bipedal and sexually dimorphic (difference between sexes) - had aped sized brains human brains re about 1450 cubic centrometres (2 and a half pints) - Austria's had about 400ml - about size of chimps
     • still present for part of Pleistocene era - used stone tools - term comes from Oldovai Gorge in Tanzania - possibly used by Austa's and early homo - technology remained unchanged for a million years (2.5 - 1.7 mil years ago

3. Genus Homo

   • appears about 2 mill years ago - larger brains in relation to body size and slower development - Palaeolithic to end of Pleistocene (1.7 mill years ago to 10000 years ago) - palaeolitich refers to old Stone Age - 95% of human technological history
     • producing cave paintings, statues etc - homo Eagaster (or homo erectus) - trainsiron in hominid life - climate got colder and more variable in Pleistocene - during this period, the brain size doubles from Austras (400 mil) to a pint and a half in ergaster - body gets larger too (males reach about 6") - developed more slowly than earlier hominids but faster than modern humans (teeth get thicker faster, enamel thickens faster) had shorted childhood than modern humans - learning probably didn't play as important of a role - tools became more complex - hand axes used to butcher carcases - fire invented
       • Homo heidelbergensis - larger brain again, more complex tools (attaching schools to sticks etc)
         • Homo neandethalensis - 600000 to 33000 years ago - discovered in neadnder valley in Germany - around at same time as homosapiens - heavier set and shorter than modern humans (cooler climates) - larger brains then us (2 and 3/4 pints) - more robust bodies - similar developmental pattern to us - may have had language - hyoid bone as possible evidence - made complex tools, hunted large prey, buried their dead, cared for their sick - few lived past 40 - whilst they were evolving in Europe, hominids in Africa were becoming like us - Homo sapiens evoled gradually in Africa
           • Anatomically modern Homo sapiens appear about 100-200 thousand years ago (or 300 according to current research - archeological evidence of modern behaviour doesn't show up until the upper palaeeolic (40-50 thousand years ago) e.g art and ornamentation - more complex shelters, built shelters, domesticated dogs, ritual burials, arts and crafts - however there might not have been a gap between the emergence of modern humans and modern behaviour e.g 130,00 year old jewellery
             • by 30 k years ago, homo sapeins are the only hominiin left - however - neanderthals interbred with early Homo sapiens - about 1.5-2.6% of DNA in non-africans due to interbreeding with neanderthals - some of the genes are associated with higher cholesterol, more belly fat, sunburns , rheumatoid arthritis and schizophrenia
               • and homo fliesienesis were still living on the island of Flores until 14 k - share many features with homo Erectus - adults stood 3 feet tall - small brains, mode 4 tools, hunted variety of animals - but are they a difference species or deformed homo sapiens?
                 • And - Denisovans - a new subspecies of H sapiens discovered in Siberia in 2010 - lived about 41k years ago and spread through Asia
                   • past debates - Piltdown man hoax 1912 - 'out of England' bias - exposed as hoax in 1953 - Dawson (discoverer) likey forger using medieval skill, orang jaw
                     • out of Africa hypothesis - h erectus evolved in Africa, modern humans evolved around 200 k years ago, 1st wave of migration to Europe from Northern Africa around 130 k years ago and 2nd wave from Southern Africa led to dispersion across world
                   • Multiregional hypothesis - humans evolves around 2 million years ago from H erectus and different populations evolved in Africa, Europe, Asia and Australasia with gene flow between them

4. Modern humans

   • little genetic variation compared to great apes - more genetic variation in Africa, consistent with African origins hypothesis - during the course of migration, humans would've gone through population bottlenecks decreasing genetic diversity - race - the human species cannot be naturally divided into a small number of distinct races - members of different races are not different in important ways - differences in races are not due to biological differences

5. Man the hunter

   • Chimp use tools and early hominids probably did too - human foregers exploit a diverse array of resources - humans rely on more hard to acquire foods than do apes - why do we eat meat? expensive tissue hypothesis - meat, especially when cooked, requires smaller guts allowing more energy for larger brains - expensive tissue hypothesis - takes many years to learn to hunt - why do men hunt - learning to extract resources requires skill, strength and detailed knowledge - older men are better hunters because they know more - most foraging societies have sexual division of labour - only possible if men and women share - men possibly stronger, but are also weak compared to other animals so this isn't great explanation - women look after kids, difficult to look after kids and hunt - hunting is high risk - food sharing extensive in humans - complexity of forging tasks may have favoured bigger brains and longer development periods