Proximate and Ultimate Causation

“Astronomy Evolution 2” by Giuseppe Donatiello (CC0 1.0)

  • Physiological adaptations and evolutionary history of the species.

Proximate Causation: a nervous system component to create a preference.  For exmaple, taste bud receptor create a preference for sugary foods due to the carbohydrate energies that they provide. Send neorons to the brain to induce a preference (neoronal). Short term, physiological explanations for behaviors.

  • Genetic Components-developmental mechanisms influence the assembly of an animal and its internal components, including the nervous/endocrine systems.
  • Neuronal Components-hormonal mechanisms develop within an individual within a lifetime. Influences behavior.

Ultimate Causation: long term, evolutionary adaptations as it is affected by descent with modification from ancestral species.

  • Adaptive Value: a behavioral trait as affected by the process of evolution by natural selection.
  • Example: mate guarding to ensure that all of a females offspring will be sired by the male.

Examples of causation:

“Prairie Voles” by theNerdPatrol (CC by 2.0)

Monogamy of Prairie Voles: neural stimulation through vasopressin is induced when the male spends time with a female- he receives positive neural rewards.

  • Proximate cause: avpr1a gene codes for V1a protein receptor– the expression of the gene influences the male to spend more time with the female, more vasopressin is then released.
  • Flow Chart:
    • The History of the Vole
    • The Internal Changes

Previous evolutionary history in the lineage leading to the prairie vole  –>  the spread of adaptations by natural selection in previous generations of the vole –> the genes that have survived to the present prairie voles –> Developmental system of young voles –> physiological system of adults, including the brain –> Behaviors including mating behaviors are influenced            –> contribution of genes to the next generation, the reproductive success of individuals  –> ev olution by natural selection continues.

“White-Crowned Sparrow” by Irene (CC0 1.0)

White-crowned Sparrows of the same species develop different dialects in different populations.

  • Causes?..
    • Possible genetic differences may affect the neural mechanisms
    • Environmental differences in Alaska and Washington may affect the experience and learning in the young males to influence their singing behaviors/dialects.
  • Research that was done:
    • Raised white crowned sparrows in the lab from the Marin and Berkeley populations.
      • Some raised in isolation- they only twittered
      • Some listened to tapes of adult male songs at 10-50 days:
        • Started singing at 150 days
        • Full song by 200 days
        • Sang the dialect that they heard, regardless of which nest they came from.
      • The data supported the idea that the young males were learning the songs through their environmental surrounding.
      • Other experiments showed that:
        • Deaf birds that could not hear themselves sing, did not mimic the song correctly. Shows the importance of hearing oneself sing.
        • Lab raised, isolated white crown sparrows will not sing songs of another species. Will only twitter.
          • Genetic composition within sparrows construct the learning system, are responsible for physiology.
        • Young white crowned sparrow can selectively store white crowned acoustical information while ignoring the songs of other species.
        • Male birds have larger song system nucleus than the female birds. The song system is called the RA and is a region in the brain that has measurable amounts of aldehyde dehydrogenase.
          • When birds listen to longer songs, there tends to be an increase in the RA size of that bird.
          • Social learning is powerful.
        • Proximate mechanisms include neurophysiology and genetic activity:
          • Part of the brain where song memories are stored
          • Part of the brain that controls sound production
          • Neural mechanisms involved in song matching
          • Flow Chart:

Key sensory (environmental) inputs –>  gene activity  –>  changes in biochemistry  –> alters neurophysiological mechanisms (song control system) –>  learning.

“Parrot” by D Coetzee (CC0 1.0)

Song Learning in Birds:Two phylogenies of song learning in birds: hummingbirds and parrots/passerine songbirds.

  • If all three of these groups were derived from a common ancester: they would have similar song control systems. Studies showed that the three groups are very similar in the RA suggesting a song learning common ancester that was lost in other groups of birds. Is more likely than convergent evolution.
  • “Hummingbird” by C Watts (CC by 2.0)

    Disadvantages to learning to sing: learning  a dialect and multiple songs is a time and energy investment.

  • Develop adaptive dialects that can be recognized easily by conspecifics so as to be more effective in a particular habitat.
    • There are differneces in Great Tit birds singing in dense forrests and open woodlands.
  • Song Matching to a Social Environment: repertoire matching allows neighbor recognition and variation in communication. The territorial success of a male depends on how many different song types he shares. The response to the focal bird will influence the future interactions between the birds.
  • Males that learn songs of particular dialects may be more attractive to females.
    • Females get information about his developmental history and suitability to a particular habitat.
      • It was found that females chose males who could copy their tutor more often than males who could not.
    • Nutritional stress in the early stages of life will affect the song learning ability of male swamp sparrows.

“Black-Crested Titmouse” by Andy Morffew (CC by 2.0)

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