Jan 7: History--Darwin

Charles Darwin: the first ethologistDarwin’s theory of natural selectionaccounts for two major phenomena thatpuzzled 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 anorganisms 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)

• Plasticity of behavior under influenceof environment and experience--again,what exactly is the trait?

• Anthropomorphism or overly complexhypotheses about other species’ behavior

• Fluidity of behavior--how to partitionthe phenotype to identify discreteevolved traits

Jan 7: History -- Anthropomorphism

Anthropomorphism: if animals act like us they must thinklike us

Morgan’s Canon:"In no case may we interpret an action as the outcome of theexercise of a higher psychical faculty, if it can be interpretedas the outcome of one which stands lower in the psychologicalscale." ( Conwy Lloyd Morgan 1894)

Principle of Parsimony

Morgan’s Canon makes the same point as “Occam’s Razor:"Entities are not to be multiplied without necessity"

What’s the problem?• Underlying mechanisms may be

different--probably are simpler

Jan 7: History -- Fluidity of behavior

Fluidity of behavior: how to partition the phenotype

A complex behavioral repertoire can often be dissectedinto components that:

• Are consistent among individuals ofthe same species (species-specific)

• Are consistent in form (stereotyped)

• Develop without the need forspecific experience (innate)

Behavioral traits as evolved“organs”

Jan 7: History -- Plasticity of behavior

Plasticity: changes in behaviorresulting from experience

• Early psychologists: notion of “instinct” was rejected infavor of environmental or cultural influences on behavior

• Darwin: “habits” (learned) vs.“instincts” (unlearned)

• Early ethologists: learning occurs, but under tightconstraints--animals have an evolved “instinct to learn”

• The debate about “nature” vs. “nurture” remains one of themost controversial issues in the behavioral sciences

Jan 7: History -- Quick history 1

Quick history of behavioral biology since 1900North America: behaviorist psychology (Thorndike, Watson,

Skinner)• Strong emphasis on environmental, or cultural explanations for

behavioral traits)

• Animals studied mainly as models of human behavior

Eddie Bauer American Legend

• In psychology nowadays, genetic influences on behavior aregiven more credit, but animals are still studied mainly asexperimental models (e.g., in neuroscience)

Jan 6: History -- quick history 2

Quick history of behavioral biology since 1900-cont’dEurope: ethology: more direct intellectual descent from Darwin• Comparative ethology by comparative anatomists (Heinroth,

Huxley, Lorenz): use natural behavioral repertoires of animals tostudy phylogenetic relationships

• This broadens Darwin's insight that behavioral traits are evolved,instinctive species-specific "organs" Example: courtshipbehavior 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 thinkabout 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

Lorenz, Tinbergen, and von Frisch were awardedthe 1973 Nobel Prize in Medicine or Physiology

“... for their discoveries concerning organization andelicitation of individual and social behaviour patterns.”

Karl von Frisch: Developed sophisticatedexperimental approach to study of sensorysystems, orientation, and communication (honeybees and other species)

Quick history of behavioral biology since 1900-cont’d

Jan 6: History -- quick history 3

Quick history of behavioral biology since 1900-cont’dThe rise of experimental ethology: “physiology without breaking the skin”

Niko Tinbergen: used rigorous experimentsto test ideas about the features of environmentthat 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

• How? ontogeny

• How? phylogeny

• Why? adaptive function

Northern mockingbird

What are the sensory, neural, and motor eventsgiving rise to the behavior?

How does the trait develop over the course ofthe animal’s lifespan?

From what ancestral traits did the behavior ariseduring the evolutionary history of the species?

What is the survival value of the trait, which favorsits maintenance in the population by naturalselection?

Alcock calls these“proximate questions”

Alcock calls these“ultimate questions”

Jan 6: History -- quick history 3

Models used by Tinbergen to study how herring gullchick knows where to peck to get food

Important concepts: sign stimulus and supernormal stimulus