Download Ch02

Animal Behavior and Evolution
(Dunbar Ch 1)
• Psychologists studied Rats…
–And made inferences about humans
• Biologists studied non-humans…
–And didn’t
• The matter of evolution and
common ancestry was ignored or
avoided
Evolution of Traits
• What is a trait?
Behaviors are traits, just like physical features.
Niko Tinbergen (1907-1988)
• Studied the flexibility of
Instincts
–Supernormal Stimuli
• Why does an animal
exhibit a trait?
–This is a question about
evolution.
Tinbergen’s “Four Whys” of a Trait
1.
2.
3.
4.
How does it change over generations?
(phylogenetic cause – Dynamic ‘Why’)
How does it change in a lifetime?
(ontogenetic cause – Dynamic ‘How’)
How does it help survival and reproduction?
(functional or ultimate cause – Static ‘Why’)
What are the environmental triggers?
(motivational or proximate cause – Static
‘How’)
Diachronic versus Synchronic Questions
Proximate view
How an individual
organism's
structures function
How vs. Why
Questions
Evolutionary
(ultimate) view
Why a species
evolved the
structures
(adaptations) it has
Dynamic view
Explanation of current
form in terms of a
historical sequence
Static view
Explanation of the
current form of
species
Ontogeny
Developmental
explanations for changes
in individuals, from DNA
to their current form
Mechanism
(causation)
Mechanistic
explanations for
how an organism's
structures work
Phylogeny
The history of the
evolution of sequential
changes in a species over
many generations
Adaptation
(function)
A species trait that
solves a
reproductive or
survival problem in
the current
environment
Tinbergen’s “Four Whys” of a Trait
• Scientific questions (Hypotheses) should
specifically address and answer only one “why”
at a time.
– Some behaviors might be by-products of other
traits (Language: Utterances+memory+T.O.M.)
– Some (“exaptations”) were selected for other
purposes but co-opted for a new one
(woodcarving, jewelry-making)
– Some may have no function at all
– Traits will interact (compete) and be tough to
tease apart (Child cries when tired)
The Red Herring of Genetic
Determinism
• Problems
–The gene for ___ problem in popular
culture.
–Genes are linked to fitness (the
probability of replication)
• However, neurons are the engines of
adaptability…and humans have a lot of the.
Determinism
• The Gene’s primary objective is survival and one
species – more than others - has evolved the genetic
trait of adaptability .
The Evolutionary Approach
• It’s not about finding causal links
between genes and behavior
• It’s about a strategic analysis of
behavior
–Why?
–What purpose could _____ serve ?
Darwin, Genes, and Behavior
• Big Considerations:
– Which behaviors are (can be) learned and which
emerge “without thinking?”
– Links between behavior and fitness (increasing
health and reproduction) are often indirect.
Almost any behavior can be linked to a “fitness”
value. How far should we go?
– Evolutionary explanations are statistical (individual
results may vary!)
– Don’t confuse causes of behavior and
consequences of behavior.
Darwinian Evolution is not Confined to
Genes
• The (genetic) predisposition for
social learning opens the door to
culture and non-genetic inheritance.
This is still Darwinian.
Our Approach, In Steps
1. Explore particular human behaviors
2. Investigate the cognitive and
physiological mechanisms that serve
the behavior (What is the influence of
development?)
3. What is the evolutionary history of
the phenomenon?
This is how Biologists do it!
• Physical form has always been explored in the
context of function; what does it do to help the
animal survive?
• We don’t have the phylogeny of behavior or
language in the way biologists have the
phylogeny of morphology.
• Comparative approaches can help, provided we
remember that the tree of life is not a ladder. A
related animal is not a direct representation of
our past selves.
Behavior is tangled in Culture
• The emergence of culture (esp. agriculture,
10,000+ years ago), through the ability to
share knowledge, may have diminished the
selective influence of environment.
• Cultural evolution, ironically, may have slowed
biological evolution.
• If so, we are stuck with a biological
adaptations that were shaped very long ago.