Download Evolution of the Human Brain

Evolution of the Human Brain
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Homo sapiens
Hominin ancestors
Chimpanzees
Primates
Evolution of Homo sapiens
Origin of anatomically modern humans
•  ~200,000 ya
•  Human population genetics
•  Archeology, Fossil record
Origin of anatomically modern humans
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Average brain size 1300 cc
Extended life history
Increased post-natal brain growth
Expanded prefrontal cortex relative to early ancestors
Lack of brow ridges, presence of chin
Behavioral flexibility
Origins of behavioral modernity
•  ~70,000 ya
•  Art, jewelry, stone tool refinement
What behaviors are uniquely human?
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Language
Abstract thinking
Art
Music
Sociality
Disorders (Schizophrenia, Autism, Alzheimer’s)
What neurological changes made us human?
•  No brain size change 200,000-70,000 ya
•  Decrease in genetic diversity
•  Need comparative data for evidence
(genetic and fossil)
Homo sapiens were not alone
Neanderthals, Hobbits and Denisovans
Homo neanderthalensis
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First hominin fossil discovered, 1856
200,000-35,000 ya
Europe, Middle East
Brain size 1420 cc
Homo neanderthalensis
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Tools, fire
Language?
Art?
Ritual burial
Homo floresiensis
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18,000 ya
Flores, Indonesia
Brain 400 cc
Tools !
Denisovans
•  40,000 ya
•  Siberia
•  Small fossil fragment only
Neanderthal brains
• Olfaction, vision, reduced prefrontal cortex
Hobbit brains (Homo floresiensis)
Comparative genomics:
Homo sapiens /early hominins
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FOXP2 – language
Brain size
Autism
Nerve development
Denisovian genes
•  8 associated with brain function or nervous system development
(NOVA1, SLITRK1, KATNA1, LUZP1, ARHGAP32, ADSL,
HTR2B, CNTNAP2).
•  4 of these are involved in axonal and dendritic growth
(SLITRK1, KATNA1) and synaptic transmission (ARHGAP32,
HTR2B)
•  2 implicated in autism (ADSL, CNTNAP2). (CNTNAP2 is also
associated with susceptibility to language disorders).
Hominin brains
Taung child (Australopithecus africanus)
•  Raymond Dart – 1924
•  Taung, South Africa
•  2.5 mya
Human - Chimp comparison
Human - Chimp comparison
•  1300 cc - 400 cc
•  Chimp lacks Broca’s
and Wernicke’s area
•  Does have planum
temporale – calls are
received but not
processed as language
Human - Chimp comparison
“ A small number of genetic changes in the expression
of genes may account for the substantial organismal
differences between humans and chimpanzees.”
Gene expression (epigenetics)
Gene expression (epigenetics)
Human - Chimp comparison
Divergent Whole-Genome Methylation Maps of Human and Chimpanzee Brains
Reveal Epigenetic Basis of Human Regulatory Evolution -
Zeng et al.
Encephalization quotient
Evolution of animal models