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Brain Evolution

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University of Lethbridge
NEUR 2600
Ian Whishaw

Brain Evolution January-16-13 11:02 AM The Monkey Trial. - Outline ○ Large number of species of hominids until quite recently and now there is only one species  Displayed especially large brains  The sophistication of tool use correlates with their brain size ○ Brain size and intelligence in modern humans  Varies greatly in size but explaining human abilities is best done by considering not size, but regional specialization. 2 Hypotheses about homo origins - Savanna hypothesis ○ Originates in Africa, the Great Rift Valley ○ Became scavengers, adapted to the new, drier climate ○ Humans can fit into the same ecological niche as lions and hyenas by developing tools to get at bone marrow ○ Periods of drying, periods of wet climate -> put pressure on scavenger animals, making them continually change - Water baby hypothesis ○ Looked at animals, that lived in the water  Compared them to humans  Alister Hardy □ In order to prove it, find the water body these animals lived in, identify how they made their living in the water, in the lakes or the water of the Great Rift valley ○ Most hominid findings - Olduvai Gorge in Tanzania  Found tons of skulls. □ Changes in hands, changes in locomotion □ Lots of changes suggesting lots of animals lived in ecological niches that required different demands Sequence of Human Evolution - Australopithicus - 6 millionyears ago ○ Southern, ape  Lots of debates about Australopithicus - Homo habilis - 2 millionyears ago ○ Human, handy  The discoverers found toolswith them - Homo erectus - 1 millionyears ago ○ Human, that stands upright  Mistakened notion that that its predecessor didn't walk upright as well - Homo sapiens - 100 thousand years ago ○ Human, wise A lotof the species living at the same time. Tim White - discovered a skull in South Africa. Found a big chunk of the body with it - Lucy (in disguise) ○ Early hominids displayed upright locomotionand tool use ○ No idea what this fossilwas, but knew it was important - Found foottracks in the ash, can tell they walked upright ○ Used a tool ○ Really tiny creatures compared to hominids themselves The Leaky Family and Homo habilis - Louis, Mary and Richard ○ First found Homo Habilis long before Tim White found Lucy ○ Toolswere much more refined Homo Erectus - Toolsbecame much more refined, could fit in their hands - Traveller During Ice Age, seas were much lower Brain and Behavior Page 1 ○ During Ice Age, seas were much lower Homo Sapiens - Best refined tools ○ Toolsthat endure like rocks are looked for ○ Females could do weaving which didn't survive Two ideas of where modern humans came from: - Out of Africa - supported by Adam and Eve genes ○ Analysis of DNA, mitochondria (power plant), come from mother, create a timeline in the female lineage. Looking at mutations in DNA, people estimated that Eve came from Africa ○ Y chromosome, same thing - Co-evolutionhypothesis ○ Supported by morphology ○ Homo erectus travelled to North America and all over, exchanging genes ○ Weaker hypothesis Other hominids… - Neanderthal, disproportionate amount of press compared to others, because they had the first skulls ○ Very modern man, almost as modern as we are ○ Up to 30 000 years ago ○ 4% of their genome can be traced A modern appearance, stouter with bigger brain. Four percent of European genes similar. - Buried their dead with flowers - Musical instruments Big surprise - Homo erectus found recently in Florenze, Indonesia ○ Homo floresiensis Brain Size - Brain size has increased steadily in the human lineage, but the biggest increase occurred Something happened between Austral and Homo. - Body size jumped - Brain size jumped - Slow and steady brain and body size increase until modern humans Why did Neanderthals die out? - Food source went away - Bigger jaw, etc EQ - Something similar was happening in the ocean when it came to brain size and EQ Theory of Brain Size - Bloodflow ○ Dean Falk, the radiator hypothesis ○ If the hu
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