Evolution of Brain and Behavior

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Evolution of Brain andBehavior

• TaxonomyDarwinian SelectionMaterial of
  Inheritance (DNA)Species ComparisonsVertebrate
  vs. Invertebrate BrainsBrain Evolution

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Taxonomic Category

• Kingdom (Animalia) Phylum (Chordata) Class
  (Mammalia) Order (Primates) Family (Hominidae)
  Genus (Homo) Species (sapiens)

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Naturalists

• Limb homology
• Early Evolutionary Theory
• Lamarcks inheritance (late 18th century / early
  19th century)

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Darwin and Wallaces Theory

• Provided theoretical explanation (c. 1858)
• Proposal for species development
• Evolution by natural selection
• Individuals differ
• Variation affects probability that offspring will
  survive
• Some differences inheritable
• Not all offspring survive

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Darwins Sexual Selection

• Sexual pressures exerted by each gender
• Anatomical
• Behavioral
• Sexual pressures favor reproductive success
• Female choice

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Modern Evolutionary Theory

• Mendels Laws of Inheritance
• De Vries mutations
• Genetics and Chromosomes
• Crick Watson
• DNA structure
• Human Genome Project

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Newer Methods Aid in ClassifyingAnimals

• Morphological molecular biology
• Convergent evolution
• Homoplasy 2 separate species  look similar
  (based on adaptation to environment)
• Homology
• Resemblance due to shared ancestry

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Comparative Animal Physiology Food Acquisition

• Food strategy correlated with brain structure and
  size
• Variable food source for rodents, insectivores,
  rabbits, primates have large brains
• Innovative strategies (car grilles, drop palm
  nuts in road) R2 with larger forebrain
• Food-storing birds have larger hippocampi

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Comparative Animal Physiology Bird Song

• 3 (out of 23) birds learn their songs
• More species than 20 orders combined
• Related to orders that inherit song
• Forebrain size correlated w/ song repertoire
• Neuronal activation (ZENK) 7 functional
  regions associated with vocalizations

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Variable Nervous System

• Use of lower species
• Less complex / dense
• Understanding of the basic plan
• Common brain areas
• Variable sizes of areas related todistinct
  functionality across species

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Vertebrate Nervous System

• Neural tube
• Bilateral symmetry
• Segmentation
• Hierarchical control
• Separate systems
• Localization of function

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Invertebrate Nervous System

• Identifiable neurons (e.g., Aplysia)
• Morphological changes (e.g., insects)
• Insect CNS similarity across variable bodyforms
  (protocerebrum, deutocerebrum,tritocerebrum)
• Nerve cord and giant axons

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Vertebrate versus Invertebrate Nervous System

• Basic plan
• Brain (trend towards increasing control over
  lower regions)
• Number of neurons (vertebrate gt invertebrate
  (larger))
• Ganglion structure
• Vertebrates cell bodies on inside, dendrites
  axons on outside
• Invertebrates outer rind of cell bodies and
  inner core of extensions (neuropil)

• Axons and conduction
• Vertebrates myelin
• Invertebrates few giant axons
• Structural changes
• Vertebrates less dramatic at development
• Invertebrates metamorphosis
• Location in the body
• Vertebrates CNS in bony skull and cord
• Invertebrates nervous system around digestive
  tract
• Constancy

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Evolution of Vertebrate Brains

• Changes in size and organization
• Brain size (encephalization factor)
• Selection pressures for increased brain size
• Survival within ecological niches
• Sexual selection (e.g., bowerbird nests)

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Take Home Message

• Taxonomy focus on phylogeny
• Darwinian Selection (Natural and Sexual)
• Material of Inheritance (DNA new way to view
  relatedness)
• Species Comparisons (variable brain sizes for
  song, foraging)
• Vertebrate vs. Invertebrate Brains (similarities
  and differences)
• Brain Evolution (competition, ecological
  challenges lead to larger brains)