Download Charles Darwin: the first ethologist

Jan 7: History--Darwin
Charles Darwin: the first ethologist
Darwin’s theory of natural selection
accounts for two major phenomena that
puzzled 19th century biologists
Continuity vs. diversity of form
• Organisms are so varied and yet the variation is
overlaid on a smaller number of basic themes
• This results from nature of evolutionary process:
descent with modification
Complexity and adaptation
• Organisms appear to be complex machines
designed to solve particular problems
• Natural selection was proposed as the agent
of design
Jan 7: History--Darwin’s insight
Darwin’s key insight for ethology:
behavioral traits are a part of an
organisms evolved phenotype
Phenotype = Morphology + Physiology + Behavior
Jan 6: History--Difficulties in study of behavior
Some major difficulties in the study of behavior
(and how Darwin and others have dealt with them)
• Anthropomorphism or overly complex
hypotheses about other species’ behavior
• Fluidity of behavior--how to partition
the phenotype to identify discrete
evolved traits
• Plasticity of behavior under influence
of environment and experience--again,
what exactly is the trait?
Jan 7: History -- Anthropomorphism
Anthropomorphism: if animals act like us they must think
like us
What’s the problem?
• Underlying mechanisms may be
different--probably are simpler
Principle of Parsimony
Morgan’s Canon:
"In no case may we interpret an action as the outcome of the
exercise of a higher psychical faculty, if it can be interpreted
as the outcome of one which stands lower in the psychological
scale."
( Conwy Lloyd Morgan 1894)
Morgan’s Canon makes the same point as “Occam’s Razor:
"Entities are not to be multiplied without necessity"
Jan 7: History -- Fluidity of behavior
Fluidity of behavior: how to partition the phenotype
A complex behavioral repertoire can often be dissected
into components that:
• Are consistent in form (stereotyped)
• Are consistent among individuals of
the same species (species-specific)
• Develop without the need for
specific experience (innate)
Behavioral traits as evolved
“organs”
Jan 7: History -- Plasticity of behavior
Plasticity: changes in behavior
resulting from experience
• Darwin: “habits” (learned) vs.
“instincts” (unlearned)
• Early psychologists: notion of “instinct” was rejected in
favor of environmental or cultural influences on behavior
• Early ethologists: learning occurs, but under tight
constraints--animals have an evolved “instinct to learn”
• The debate about “nature” vs. “nurture” remains one of the
most controversial issues in the behavioral sciences
Jan 7: History -- Quick history 1
Quick history of behavioral biology since 1900
North America: behaviorist psychology (Thorndike, Watson,
Skinner)
• Strong emphasis on environmental, or cultural explanations for
behavioral traits)
Eddie Bauer
American Legend
• Animals studied mainly as models of human behavior
• In psychology nowadays, genetic influences on behavior are
given more credit, but animals are still studied mainly as
experimental models (e.g., in neuroscience)
Jan 6: History -- quick history 2
Quick history of behavioral biology since 1900-cont’d
Europe: ethology: more direct intellectual descent from Darwin
• Comparative ethology by comparative anatomists (Heinroth,
Huxley, Lorenz): use natural behavioral repertoires of animals to
study phylogenetic relationships
• This broadens Darwin's insight that behavioral traits are evolved,
instinctive species-specific "organs" Example: courtship
behavior in ducks
Jan 6: History -- quick history 2
Quick history of behavioral biology since 1900-cont’d
• Konrad Lorenz: continued this tradition, and also began to think
about internal aspects of behavior
• “Fixed action pattern” (FAP) as unit of behavioral phenotype
• Lorenz also hypothesized about motivational triggers of FAP
Jan 6: History -- Nobel Prize
Quick history of behavioral biology since 1900-cont’d
Karl von Frisch: Developed sophisticated
experimental approach to study of sensory
systems, orientation, and communication (honey
bees and other species)
Lorenz, Tinbergen, and von Frisch were awarded
the 1973 Nobel Prize in Medicine or Physiology
“... for their discoveries concerning organization and
elicitation of individual and social behaviour patterns.”
Jan 6: History -- quick history 3
Quick history of behavioral biology since 1900-cont’d
The rise of experimental ethology: “physiology without breaking the skin”
Niko Tinbergen: used rigorous experiments
to test ideas about the features of environment
that animals respond to
• Earliest example: Egg-rolling by goose
• Pioneered use of physical models to probe
mechanisms of behavior
Jan 6: History--4 questions
Tinbergen’s four questions
• How? physiological causation
What are the sensory, neural, and motor events
giving rise to the behavior?
• How? ontogeny
How does the trait develop over the course of
the animal’s lifespan?
Northern mockingbird
• How? phylogeny
From what ancestral traits did the behavior arise
during the evolutionary history of the species?
• Why? adaptive function
What is the survival value of the trait, which favors
its maintenance in the population by natural
selection?
Alcock calls these
“proximate questions”
Alcock calls these
“ultimate questions”
Jan 6: History -- quick history 3
Models used by Tinbergen to study how herring gull
chick knows where to peck to get food
Important concepts: sign stimulus and supernormal stimulus