Evolution and Human Survival

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					Evolution and Human Survival


          Lecture 4
          PSY391S
        John Yeomans
      Diversity of Life Forms
• Categorization by phenotypes.
• Linneaus: Species, genus, family, order
  class, phylum, kingdom.
• Which features are most important in
  making groups?
• Can the same principles be used to make
  other groups?
• How were these groups formed?
      Diversity of Ancient Life
• Geology: Older fossil forms in deeper
  sediments.
• Changes in size, structure and design
  imply family histories. Evolution.
• Variety of habitats and fossils. Beagle.
• How did species evolve over millions of
  years?
• Darwin: “Survival of Fittest”
        Evidence for Theory
• Historical Record: Wars, famines, diseases,
  habitat lossselection.
• Movement of species to new habitats
  new structures, e.g. lungs, legs, hair.
• How did this happen in prehistory?
• Selective breeding of domestic animals--
  pigeons, cows, dogs.
              Speciation
•   Finches in Galapagos--Darwin and
    Grants.
•   When do phenotype differences become
    species differences?
•   How did humans diverge from primates?
•   Why did Neanderthals or other primates
    die?
            How to Survive?
• “We are the accumulation of mechanisms that
  allowed our ancestors to survive and to
  reproduce their genes” (Sagan)
• “Accumulation” includes functional and vestigial
  systems. DNA also an accumulation.
• Who were our ancestors who managed to
  survive and reproduce?
• The Selfish Gene: All our systems and strategies
  are shells for helping our genes survive.
• Biological Purpose of Life?
         Human Strategies
• Survival: Kill others genes and save your
  own? Humans survive by social
  cooperation rather than “dog eat dog”.
• Reproduction: Have the most offspring
  possible? Humans have the fewest--single
  births, long immature period--but highest
  survival rate.
• Learning and specialization--Civilization.
• Aggression? Yes, but not to disrupt social
  organization.
Classification and Gene
        Lineages
        Lecture 5
        PSY391S
      John Yeomans
   Classification by Phenotype
• Which features are most important? Little
  agreement.
• Principles of comparing different groups?
• Where is change from species to genus to
  family etc, if evolution is continuous?
• Genes are more fundamental, in theory,
  than any surface features.
• Quantitative rather than qualitative.
      Classification by Genes
• Hybridization of DNA samples (Wilson).
• Complete sequences, genomes.
• Similarities in genes from flies to humans
  imply common lineages.
• Reconstruction of family trees: Are all
  bases equally important?
• Is DNA mutation rate constant?
• Genetic Clock~ 1%/5 million years.
      Human Family History
• Females: Mitochondrial DNA is preserved
  from mother to daughter. 16,569 bases.
• Trace human origins to Eve?
  Neanderthals?
• Males: Y chromosome is preserved from
  father to son. Trace family lineage.
• Trace DNA in all humans to extract
  lineages around the globe.
           Human Genes
• Which DNA makes us different from
  primates? E.g. prodynorphin.
• Are some genes more important?
• Which genes affect hands, brain, speech?
• Could a few genes lead to larger brains?
  CNS Evolution--Invertebrates
• Nerve nets: Action potentials, reflexes.
• Ganglia chains: Molluscs, worms,
  arthropods.
• Giant neurons and axons--no myelin.
• Head ganglia are fused.
    Lecture 6: Evolution of Brain


•   Mammalian brain properties
•   Brain size vs. body weight
•   Ancient brains--when did they get bigger?
•   Human brains--when did they get bigger?
           Vertebrate CNS

• Protected brain and spinal cord.
• Myelinated axons saves space for more
  neurons.
• Shift from midbrain, cerebellum and
  olfaction to limbic system then cerebral
  cortex.
Brain Size and Body Weight
               Equation
• Log Brain Weight=0.7(log Body Weight)+b
• Or: Brain Weight = K(Body Wt)0.7
• Power function linear on log-log plot.
• Some mammals have extra brain size
  (Humans and dolphins 8X extra)
• K = encephalization factor.
All Vertebrates
        Ancient Vertebrates
• Brain weight from endocranial space.
• Body weight from leg bone diameter.
• Ancient reptiles same as modern reptiles,
  except for Archeopteryx (bird-like
  predator).
• Modern birds and mammals increased
  brain capacity by 4X over ancient birds
  and mammals (still 4X reptiles).
• Warm blood favors brain evolution?
Encephalization
    Evolution of Human Brain

• Increased by 3X about 1-2 million years
  ago.
• Most of change in frontal cortex.
• Neoteny: Do we sustain embryonic brain
  growth for longer by keeping neonate
  features?

				
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