Transcript Learning behavior

Change topic
• Enough on Proximate causes, interesting and a lot
of work.
• Basics: Stimulus: effector: in between: behavior
• What we will look at now is the behaviors
themselves! Will drift back to proximate causes
but main focus will be behaviors
• First distinguish between two major categories of
behavior: Innate (instinctive) vs Learned
Innate behaviors
• Used to make sharp distinction between
innate and learned behaviors.
• Innate: as instinctive indicates, behavior that
is “born with you” and can manifest itself
without learning it.
• First proposed by Konrad Lorenz early 1900’s
Fixed action pattern
• One of the standbys of innate behavior was the
“fixed action pattern”
• Defined as a behavior, once stimulated to start
will continue to its end, even if the original
stimulus (innate releasing mechanism)removed.
• Greylag goose of Lorenz. Used to be the Classic
example!
• Now, hardly
heard of!!
Innate behavior
• Why??
• Lot of controversy over this concept and in fact
can’t even be found in many new books!
• Here we touch on it for both historical reasons
and just in case it becomes in fashion again!
• Fairly stereotypic behaviors within species and
across species.
• Would manifest itself in isolation, no outside
environmental influence, or at least we think so!
Innate Learning
• Many argued that can’t isolate from all
possible environmental influence, so can
never be sure….
• A lot of circular arguments made: graduate
students trying to make a name for
themselves!
• U.S. vs Europe (reductionist vs holistic)
• Yet we do recognize that behavior has a
genetic basis!
Innate behaviors
• And that where it stands to day, so far… most
accept that behavior has genetic basis (or at
least control!!), just arguments as to how
much!!
• What are you to do?
How to view innate vs learning
• Best visual model is: all born with a
framework (skeleton) of behaviors or
behavioral capabilities: a lot due to anatomy
and physiology: a dog may want to climb a
tree but it will never learn how to do it!
• This defines the range of possibilities. The
actual behavioral repertoire (fleshing out of
skeleton) individual develops depends on
experiences (learning) it has.
Phenotypic plasticity
• Some equate it to “phenotypic plasticity”
• Ability to change phenotype under different
environmental conditions.
• Example Bryozoans (spines in presence of
predators but not in absence)
• Example Locust (solitary vs migratory types:
different structure AND different behaviors!)
• Maybe Lamarck was right!!!
Behavioral plasticity
• Behaviors are more changeable than anatomy
or physiology!
• Although the behavior itself may not be
genetically transmitted, the ability to do so is
AND as we will see, can be transmitted
socially.
• Still all quite confusing!! Mental gymnastics!!
Blah Blah Blah….
• What we do know for sure is that behaviors
CAN change with experience, animals can
learn.
• So now looking at those modification from
experience: learned behaviors (Chap. 4)
Learned Behaviors
What is learning
• First must address the question of what do we
mean when we talk about learning?
• Or definition of learning:
• A relatively permanent change in behavior as
a result of experience.
• One could argue: where did that original
behavior come from?? Innate, Genetic?
• Lets not go down that road!!!!
Learned behaviors (chap 4)
• Best to start with the behavior that enables
many others: Learning behavior
• Identified earlier as a source of gaining
behaviors
• Is a behavior in itself!
Individual learning
• Make a distinction between how an individual
learns from experience and social learning,
learning from other individuals.
• Here we deal with individual learning
• Three interrelated question:
• 1) How do animals learn
• 2) Why do animals learn
• 3) What do animals learn
How do animals learn??
• Psychologists: processes underlying learning.
• Three types of experiences that lead to
learning
• 1) single stimulus
• 2) Stimulus-stimulus
• 3) response-reinforcer
Single Stimulus
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Single stimulus given an animal:
E.g. blue stick to a rat in a cage.
Rats will notice because of novelty.
If consistently notice it: call sensitization to
the stimulus
• If eventually ignores it: called habituation.
• Two possible learned responses to a stimuls
Single Stimulus
• Sensitization is good If stimulus is important and
may help animal associate this stimulus with
other cues.
• Habituation is good in that it helps reduce the
background “noise” (bombarded with stimuli
constantly) and enable response only to those of
importance
• Can be disadvantage if become habituated to a
cue that later becomes important! Predation e.g.
Stimulus-stimulus
• Here we see how an animal related TWO
stimuli
• Example: pair blue stick with odor of a cat.
• Cat reacts to odor initially but…
• Eventually will hide just when blue stick is
spotted: associates blue stick with cat..
• Pavlovian or classical conditioning.
Terms…Terms..Terms!
• Things getting complicated so need terms to keep
it straight!
• 1) First stimulus: Conditioned stimulus (in itself,
does not elicit a response
• 2) Second stimulus: Unconditioned stimulus (this
is one that would normally elicit a response, even
without training.
• 3) Conditioned response: This is reaction of
animal to conditioned stimulus AFTER it has
associated it with unconditioned stimulus
Terms…terms…and more terms!
• A few more terms associated with this.
• 4) Appetitive stimulus: stimulus that is
considered positive, pleasant, or rewarding,
e.g. food, potential mate, safe haven, etc.
• 5) Aversive stimulus: Opposite – unpleasant,
e.g. shock, noxious odors, etc.
• 6) Excitatory conditioning: positive
relationship – first stimulus leads to or
predicts the occurrence of the second
And more…..
• Inhibitory conditioning: If first predicts
second event will not occur: Huh?
• E.g. if blue stick becomes associated with NOT
getting food when rat would normally get it.
• No blue stick, will get food.
• Blue stick, no food.
• Can add second and even 3rd and 4th
conditioning stimuli!!!
What does this all mean!!???
• Basically it means that animal can associate
one stimulus with others AND to predictable
outcomes (presence of cat, getting food or
not….)
• Through this association it “learns” how to
modify its behavior
• So the ability to associate stimuli with
outcomes is important part of learning
behavior.
here
Response-Reinforcer
• This associate ability becomes more evident in
third type of experience.
• Commonly called: Instrumental conditioning
or Operant or Goal-directed learning.
• Response of animal is reinforced by a reward
or punishment
How different from Pavlovian?
• Animal takes some action first, stimulus comes
second. Associates outcome with stimulus rather
than stimulus with outcome
• Classic is rat pushing lever to get food.
• Can get complicated!
• Law of effect: If response in presence of stimulus =
satisfying event: association between stimulus and
response strengthened. And visa versa!
• Skinner and “Skinner box” biggies in this area
Summary on how they learn
• Why is this all important?
• We know animals (us!) learn from experience.
What we need to know is how is that
accomplished?
• This then helps us understand how, why, and
when certain behaviors may occur
Summary
• Results so far: A feedback system where,
• 1) animal does something and gets a result
and it remembers this
• 2) something happens to animal and it
remembers circumstances (stimuli) under
which it happened
• So two biggies: association AND Memory!
• How memory works, is anyone’s guess!!
Memory
• Without it learning is impossible
• Still don’t know exactly how we physically
store info, some three dimension electrophysical process!!??/
• What we do know is:
• Memory is selective! (extinction curves)
• Memory capabilities vary intra and interspecifically: some better than others
Memory
• Brain-memory-learning is the main genetic
link between genes and behavior.
Why animals learn
• Ok, some idea of learning process: carrot and
stick!
• Why do they learn?
• Simple answer is that it has a “survival
advantage”
• But not as simple as that or is it??
Why learn
• The fact that memory is selective can provide
clues:
• - Receive thousands/millions of stimuli
• - Make thousands of associations
• - Some we remember/others we forget
• - Some we remember longer than others
• Reflects importance of the associations with
environment
Why animals learn?
• Behavior is interface of animal with its
environment: a changing environment!
• With this interface, animal needs to capture
energy and avoid loosing it!
• In capturing energy (food), learning important
way of increasing foraging efficiency – reduce
foraging time
Why animals learn
• In capturing “new energy” (reproduction),
learning increases chance you will participate.
(not just trees releasing pollen!).
• In avoiding loosing energy, it is helpful to learn
what are safe vs dangerous areas!
So why do they learn?
• Helps maintain the energy capturing machine
under environmental conditions.
• Indeed if they do not learn, they are dead
meat!!!
What do they learn?
• Ok, out of those millions of stimuli and
associations, which, if any, are important to
learn about??
• Obviously rest of book is on the different
behaviors that have developed based on
stimuli received!
• Here is a general treatment of the major
categories, which we will then look in detail
later.
What do they learn?
• List of things important to their survival!
• 1) learning where home is located!
• What this involves is all the various behaviors
we will cover in Chapter 13!
• As mentioned, behaviors are interface of
animal with its environment
Call Home!!!
• Animals live in the environment and so it is
important to learn about it.
• Bird and other migrations: learning migratory
routes
• Habitat selection: learning what is the
appropriate habitat to live in!!
• Will see this is one of THE most important
behaviors to learn for many species!
What else?
• 2) Learning about your mate!!!
• Obviously important for the capture of future
energy for the species!!
• Two chapters devoted to this!! (6 & 7)
• Need I say more??
Next on the list…
• 3) Learning about familiar relationships (Chap
8 & 9)
• Related to the previous one.
• Getting into social behaviors
• Interfacing with others of the same species.
• Recognition, cooperation, etc.
• We have to “deal” with relations!!
Next?
• 4) Foraging!! Looking for the energy that
keeps us alive!! (chap 10).
• 5) Closely related is anti-predatory and
predatory behavior (Chap 11). Learning how
to avoid being eaten can come in handy!
Still more
• 6) Aggression: (Chap 14). Learning how to be
and when to be aggressive has survival
advantages!
• 7) Fear! Not listed but is a very helpful
behavior to learn, especially in anti-predator
context!
• 8) Play (chap 15) what is its role?
So there
• As mentioned, these cover in a broad sense all
that an animal learns and as we will see all
play a role in aiding in the survival of the
individual and the species.
• Before we go to these behaviors, need to
cover that other form of learning: Cultural
transmission
Cultural transmission (chap 5)
• Talked about how an individual learns from
external stimuli
• What good is learning something new if you
can’t share it!!
• Why share it? Can aid in survival of relatives!!
So sharing info has a survival advantage for
your genes!!
Cultural transmission
• This sharing of information is cultural
transmission.
• Defined: Transfer of information from one
individual to another via social learning or
teaching (can be within or across generations)
• As mentioned: this is a form of evolution
without genes!
Cultural transmission
• Form of learning: social learning
• Obviously similar to individual learning in
terms of pathways, etc.
• But involves learning from others
• Lots of non-human examples:
• Japanese macaques most noted
• First was when one female learned how to
wash her potatoes to remove sand and dirt
Cultural transmission
• Others followed suit and began to wash their
potatoes.
• Since then many more incidences noted.
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Characteristics of cultural transmission:
1) can spread quickly
2) more likely to spread to younger ones
3) seems to be some resistance to adapt in
older individuals!!
here
Importance of cultural
transmission
• How does it differ from individual learning?
• Individual is often trial and error
• In cultural transmission, emphasis is:
individual to individual
• Way of transmitting individual learned
behaviors, even after initial learner has died
• Way of building on experiences: one learns
and transmits a behavior, others improve it
Social learning
• As mentioned, basis of cultural transmission is
social learning.
• Various forms of social learning, two common
ones are Imitation and copying
Imitation
• Must involve new behavior learned from
others and must involve new spatial
manipulation: Macaque and potatoes.
• The keys are a new behavior and then
undertaken by learner elsewhere
Copying
• One animal repeats what it sees the other do.
• Differs from imitation in that need not be a
new behavior.
• Subtle difference but…
Teaching in animals
• So far, talking about an animal being observed
doing something and then it is imitated or
copied by others
• No intent on the first animal (the model) in
transmitting this information, passive role
• Evidence that many animals take active role in
transmitting information: Teaching
• Implies one acting as instructor and others
acting as students.
Teaching in animals
• Teacher must provide immediate benefit to
students but not to itself.
• Must “teach” only to naïve individuals
• Must impart new information faster that
students might otherwise receive it.
Examples of teaching
• Female cat bringing live prey to young
• “helper” meerkats removing stingers from
scorpions and then letting young catch and
eat them
• Many more usually females “teaching” their
young.
• This is a common theme found
Other commonalities?
• Usually are either “opportunity teaching” or
“coaching”
• Opportunity teaching: teacher places student
in situation conducive to learning
• Coaching: Teacher directly alters behavior of
students by incentives.
What next?
• Modes of cultural transmission (direction of
the transmission)
• 1) Vertical
• 2) Horizontal
• 3) oblique
Vertical cultural transmission
• Information is transmitted across generations
from parent to offspring.
• Examples: Lots! All that “kids” learn from
parents
• Male birds learning song from good old dad
• Females learning song preferences from mom!
Horizontal cultural transmission
• Learning from your peer group: Many animals
segregate based on age (like humans!) and
information is passed among them.
Oblique transmission
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Across generations but not parent/offspring
Young get info from nonparent adults.
Common in species with little parental care
Many of our fears seem to be acquired this
Summary
• Cultural transmission is a way of passing
information on to other individuals
• Avoids reinventing the wheel
• Way of improving the wheel!
• Can be done passively: social learning
• Can be done actively: teaching
(opportunity/coaching)
• Occurs along different pathways:
Vertical/horizontal/oblique
Next: communication behavior
(Chap 12)
• Why we jumping ahead?
• Saw that a lot is learned via cultural
transmission
• This transmission includes sight AND sound!
• So, logically next behavior to consider would
be communication!
• Communication includes sight and sound
Communication behavior
• Defined: transfer of information from a
signaler to a receiver.
• Many of the communicative behaviors are
part of the larger behavior we will be looking
at: stress calls are part of “anti-predator”
behavior
• Will not concentrate on the overall behavior
(which we will cover more in detail alter)
• But the role communication plays in it.
What is important?
• Is it honest??
• Are the individuals accurately conveying
information or are they trying to manipulate
others?
• Not just a problem with humans!!
Honesty
• Answer is yes and no.
• Sometimes communication is “honest”,
conveying correct info
• Sometimes use communication to “get what
you want”!
When to be honest?
• Classic ethological approach: both parties will
be benefiting from information exchange
• With this, less exaggerated signals
(conspirational whispers)
• Should be used in kinship communication
• Unrelated, often hard to envision when both
would benefit.
• Should occur when impossible to fake
information: Toads, only large males can make
deep croaks
• When costly to fake: length of song, energy
intensive and only healthy ones can do it.
When to lie!
• Dawkins and Krebs suggested: most times!!
• Communication in general is to convince
recipient of something.
• Advantage to “beefing up” our resume!
• Selective advantage to convincing recipient
you are something more than what you are.
• Typified by exaggerated signals
Recipient??
• Puts pressure on recipient!
• Selection for those who can see through the
lie!
• Mind readers and arms race
• The better recipient gets at detecting a fake,
the better the fake has to get!
Summary on honesty
• Communication behavior is to convey info
between signaler and receiver
• Honesty may not always be the best policy
• If send dishonest information, initiates an
arms race
• Depends on what trying to communicate
• AND cost/benefit to honesty or dishonesty.
Reasons for communication
• Book: effort to solve problems that animals
encounter in natural environment
• Help see costs/benefits to communication
• Three main problem areas:
• 1) foraging
• 2) mating
• 3) predation
Foraging communication
• Problem: how to coordinate group foraging?
• First… Why?
• Social species easy to see: work as group and
can more efficiently use a food source
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Not so social species?
Cost/benefit
Cost: you have to share food!
Benefit: if you are “recruited” to food source.
Benefit: Recruiter? Keep track of food source
if you have to leave and food source moves.
here
How coordinate?
• Special food calls: many species of birds signal
food source by calling
• Crows:
• Swallows
• Physical movements
• Waggle dance in bees
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Chemical/vibrational communication: ants
Recruitment phermones:
Methyl 4-methylpyrrole-2-carboxylate
3-ethyl-2,5 methylpyrazine
Placed along trails
• Vibrational communication
• Stridulation: Moving the ultimate body
section (Gaster) up and down.
• Found this conveys info to others about leaf
quality.
Problem: how to find a mate?
• As mentioned 2 chapters on this but here we
look at it relative to communication behavior
• Two main communication pathways are:
• 1) vocal
• 2) tactile
Vocal communication and mating:
bird songs
• Many species use vocal communication to find
and attract a mate
• But birds seem to have brought it to a well
defined level: frogs croak, elk bugle, but birds
sing!
• Some simple but many quite complex
• So will look at them as an example
Birdsongs
• Used for many things species can have one,
10, 100, a 1000 different songs.
• But here we concentrate on those used for
mate selection
• Question: How songs are used to attract a
mate.
• Question: Why does it work??
Genetic filter
• Thought that songs are a genetic filter females
use to select mates.
• One filter may be the number of songs a male
can sing! The more songs, the more
successful he is!
• Why? More songs: older male or more fit to
sing them! Harder to fake!
• Remember, in communication receiver is
trying to detect fake!
Song complexity
• Another filter is song complexity:
• Evidence suggests that it is not what you say
but how you say it!
• Frequency, amplitude, rate of pauses,
maximum note length, etc. All important
components that transmit information about
mate suitability
• More energetically costly, more likely song is
honest.
Tactile communication and mating
• Water striders: produce ripples in water with
their legs.
• Like songs, produce different ripple
frequencies and amplitudes for different
communication.
• Calling mates; courtship: sex discrimination,
etc.
Ripple communication
• Each is different, travel across the water and
interpreted by females, which then respond
accordingly!
• How they use these to determine whether
sender is honest or not, not clear yet but likely
similar to sound waves of songs
Problem: warn others about predators
• When feeding in groups is beneficial, would be
nice to warn others of impending danger!
• Problem is: how, when, and why
• How: mostly vocal calls (alarm calls)
• Have the advantage of being very specific and
can be transmitted rapidly
When do you warn others?
• Studies of birds show not always!!
• Often only intersexual: mates will warn
partner but not others of same sex!
• Mate investment
• Put a value on who to warn!
• Indicates the potential “Why”
• - when there is potential advantage to you or
your genes!
Honesty and alarm calls
• We would assume that alarm calls would be
“honest”
• Most cases they are, transmitting important
information
• However, in some species we find alarm calls
being used in a deceptive manner
• The boy who called wolf!!
Deceptive alarm calls
• When would it be advantageous to use a
deceptive alarm call?
• Vervet monkeys: low ranking males will do so
in potentially dangerous intergroup
encounters: to avoid a fight!
• Male swallows will do so if they see their mate
with another male!!
Does it work?
• Initially yes!
• But like the little boy, if you do it too often,
others will ignore you.
• Ground squirrels: If not backed up by seeing
predator,
will ignore calls
How many false alarms should it take!
• Obviously there is a danger in ignoring an
alarm call: IF the villagers would have listened
that last time….
• But how many false alarms are needed?
• Depends on danger level, kind of like mimicry:
• Depends on sender! Others may get to know
one is unreliable.
Summary communication behavior
• Important in transmitting information to
others.
• Can be honest: what you say is what is so.
• Can be deceptive: trying to manipulate
• Is used to solve problems individuals face.
• Depending on problem, depends on degree of
honesty.
• If dishonest, can start evolutionary race!
Next: sexual selection (Chap 6)
• Ok, have basic behaviors covered, innate,
learning behavior, communication, etc.
• Ready to look at “specialized” behaviors
• Ones designed to deal with specific aspects of
an individual’s life.
• Again, remember will be a lot of overlap and
at times may seem repetitious.
• Can’t pigeon-hole behaviors
Sexual selection
• First we will deal with is behaviors aimed at
acquiring more energy for your species:
reproduction.
• Various aspects of it, first is selecting who you
will do it with!!
• Believe it or not: don’t want to do it with just
anyone!
Gene selection
• Reproduction is for passing on your genes
• Evolutionary advantage to do it wisely!
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When we talk about sexual selection
Consider:
Intrasexual selection: same sex competing
Intersexual selection: selecting mate
Intrasexual selection
• Darwin: competition for mates important part
of reproductive success!
• For most species: males do the competing, at
least we think so!!
• Why?
Male competition
• Why:
• Males produce millions of sperm and can
potentially inseminate many females at a low
energy cost.
• Females: produce 1-<15 eggs/cycle and
although can and do mate with more than one
male, really only need one male to fertilize
eggs.
• Also, energy intensive post fertilization
here
Bateman’s principle
• 1) females should be choosier be eggs
expensive to produce and reproductive
success limited compared to male
• 2) should be greater variance in reproductive
success of males.
Because there is an evolutionary advantage to
being a successful male, evolution would favor
competing for success.
How do they compete?
• Many forms: familiar with many
• Direct fighting is common
Male Competition
• Displays: birds good at this!
Mate choice
• However, not all just male competition.
• What is the female’s role?
• Used to think it was passive: waiting patiently
on the sideline to see who the winner would
be!
• But females have stake in this!
• More so than males: it is their ONLY chance at
passing their genes on!
So who is choosing whom?
• Answer: both really.
• So we now talk more about Mate choice
• we look more not just at the glamorous
battles/displays of the males but more at the
often subtle reasons WHY males do what they
do, which is often driven by female choice!
• Colorful male birds!
Male secondary sex characteristics
• Why do male lions have a mane?
• Why do male baboons have such red butts!!
• It is because it is what it takes to convince a female!
So who is doing the choosing??
• Mate choice is a male trying to convince
female he is the right one and females
evaluating IF that is really the case!
• So we need to look at evolutionary models of
mate choice to better see how and why we
males have gotten so ridiculous!!
Evolution of mate choice
• Past: looked at flashy males
• Today: lots of research into female choice
• Underlying assumption of most earlier work is
that female choice is under some genetic
control – there is genetic variation in female
mate choice behavior.
• Four evolutionary models proposed:
Evolutionary models
Direct Benefits model
• Natural selection favors females who are
genetically predisposed to choose mates that
provide benefits beyond just good genes.
• Female will choose mate that provide
important resources: food, safe shelter,
assistance, etc.
Evidence for this model
• Female scorpionflies: choose mates based on
the size of prey item they bring. The bigger
the better, if you don’t bring anything, you get
rejected!
• Nuptial gifts: she eats while they copulate.
More
• Female determines how long they copulate
based on size of nuptial gift: again, larger
longer
• Longer they copulate, more sperm transferred
• What does she get from all this?
• Larger gift, longer copulation time, more eggs
produced.
• Also provides a meal for her!
Genetic link
• Strong selection pressure on males who can
bring large nuptial gifts.
• Finding large gifts is time consuming and
dangerous.
• Few can do it, so they do the most mating
• Some steal prey by mimicking females
• Evidence that females select males based on
resources provided and how it can affect male
foraging behavior.
Good genes hypothesis
• Concentrates not on resources females get
from males but the quality of the sperm they
receive: good genes!
• Good genes: those that code for some suite of
favorable traits, which are passed on by a
choosey female.
• More indirect benefits than previous
• Increased survival of offspring
But…how do you tell?
• May sound good and field evidence that
females selecting for other than direct
benefits.
• E.g. Pronghorn, females select male based on
size of harem…larger he is able to keep, more
“attractive” he is.
• But how do females know this is good
genetically??
Basic questions
• 1) How can females determine which males
have “good” genes?
• 2) If she is using some criteria, how does she
know the male is not faking this criteria??
That communication thing again!
Honest males, do they exist?
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Answer the second question first.
Saw in communication behavior
Selective advantage to a male being dishonest
But…selective advantage to female who can
tell the difference!
• Arms race that should lead to Honest
indicators of gene quality…but what are they?
Honest indicators of gene fitness
• In general two major factors hard to lie about.
• 1) survival capabilities
• 2) physical health
• Can be related and both are energy intensive.
Survival capabilities
• How do you tell that your potential mate can
give you genes that would enhance survival of
offspring?
• You test them!!
• Not surprising that for many species, males
have elaborate courting rituals.
• Many related to health as we will see.
• But some are tests of survival.
Survival tests
• Usually say brightly colored male birds are so
to “attract” a mate.
• Why attractive? Assume is a good indicator of
health.
• But, could be a test against predation!!
Survival test
• Elaborate courtship rituals:
• Brightly colored, singing, and dancing like a
fool!!!
• If you can survive predation attempts, you
may have what it takes!
Survival
• Frogs, fireflies, list goes on and on of males
putting themselves in danger to attract a
mate. Why?
• You would think that evolution would favor
safer courtship rituals unless its demanded by
the females!
State of Health
• Majority of courting rituals (usually male-male
competition) can be considered ways females
can judge health of potential mate.
• Not surprising that many involve physical
contests.
• Definite filter regarding
health of male and hard
to fake.
Physical contests
• Leks in grouse, contest for preferred central
areas: physical strength.
• AND safety for females for mating!
State of Health
• Brightly coloring
• Takes energy to produce AND maintain all this.
• What is the first thing to go when you feel sick?
Personal hygiene!
• So two tests:
• 1) do you have genes to
grow them/
2) Are you healthy enough
to maintain them?
Bright colors
• Redwing black birds:
Bright colors
• Bright colors may indicate parasite resistance;
Sticklebacks
Courtship rituals
• Besides putting yourself in danger, it takes
energy to dance around, hop up and down,
sing, build things (bower birds).
Odors!
• Evidence some females use odors as indicators
of health – good genes.
• MHC: Major Histocompatibility complex
• What?
• Set of genes related to disease resistance
• These are “good” genes to get!!
• Combination of genes in this complex result in
different body odors!
MHC
• Found males with dissimilar MHC
combinations were more attractive to females
• Also, different odors related to number of
genes in this complex and females attracted to
males with higher numbers of genes!
here
Symmetry
• Symmetry of body form: similarity of left and
right sides.
• Related to developmental stability
• Which is related to ability to adapt to change.
• Obviously equating health with genetic well
being.