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Brain evolution


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Brain evolution

  1. 1. Brain Evolution
  2. 2. There is something unusual about the human brain and its behavioral capacity The neocortex is disproportionately large in humans
  3. 3. Neuroscientists have paid rather little attention to the study of brain evolution Neuroscientists
  4. 4. Clade
  5. 5. Theories are highly speculative There is a single goal or direction to evolution Misconceptions about Brain Evolution Brain Evolution Neuroscience
  6. 7. Interestingly, domestic animals with our efforts to improve a wild stock, generally have reduced brain size.
  7. 8. Butthead
  8. 10. Tarsiers
  9. 11. Neocortex Origins Not that new at all. Similar to the Dorsal Cortex in birds and reptiles
  10. 12. V. Dorsal Cortex Neocortex
  11. 13. Ancient Neocortex were likely to not have the differentiated layers and neuron types
  12. 17. Evolution of Primates: The early years
  13. 18. Evolution of Primates: Improvements
  14. 19. Old and New world monkeys developed their trichromatic vision separately.
  15. 20. Tarsiers and Owl monkeys are secondarily nocturnal
  16. 21. Hominines and Chimpanzees
  17. 22. Early Primates Early primates were lemur-like in body form, and their brains were shaped like those of present-day lemurs, although smaller.
  18. 23. Somatosensory Cortex VP S1 S2 Ancestral State Derived State V3 DM MT V1 Visual System
  19. 24. Most of the large number of specializations that likely evolved in early primates or their immediate ancestors
  20. 26. Evolution of Hominin Brains Human brains are not symmetrical in shape, so that the planum temporale, the sheet of cortex on the lower surface of the lateral sulci, is usually larger in the left cereberal hemisphere than on the right.
  21. 27. Interestingly, however, great apes exhibit the same asymmetry of the temporal lobe as humans, despite their lack of language.
  22. 29. Australopithecus ~600 cc Homo habilis                     ~800 cc
  23. 30. Homo erectus ~1000 cc Homo sapiens ~1400 cc
  24. 33. The issues of a Big Brain Inverse Ninja Law: The more ninjas there are, the weaker each individual ninja is Selection has to be based on a few developmental mechanisms Higher metabolic cost may require better diet .
  25. 34. Large brains generally devote much more of their mass to connections. Small morphological adjustments dramatically change the area affected.
  26. 36. Primates brains simply have many more neurons than rodent brains of the same size