coefficients of relatedness (r-values) of descendant and non-descendant kin
descendant kin:
- offspring: r = 0.5
- grandchildren: r = 0.25
- great-grandchildren: r = 0.125
non-descendant kin:
- full siblings: r = 0.5
- half-siblings, nieces and nephews: r = 0.25
- first cousins: r = 0.125
altruism
a type of cooperative behaviour that increases the recipient’s fitness, at the cost of the actor’s fitness
onset and decline of sensitive periods
onset of sensitive periods:
- triggered by external stimuli and development of the nervous system (ability to perceive stimuli)
decline of sensitive periods
- maturation triggers hormones to signal the end of the sensitive period
- ends when an individual achieves a goal (e.g. young birds stop learning to sing when they have successfully learned the song)
evolutionarily stable strategy (ESS)
behaviours that persist in a population over time
sensitive period
a critical period in an organism’s development, during which the nervous system is especially sensitive to certain environmental stimuli
Hamilton’s rule
an altrustic allele will spread if the benefit to the recipient is greater than the cost to the actor
Br - C > 0
- B = benefit to recipient
- r = coefficient of relatedness; the relatedness between the actor and recipient, measured as the proportion of alleles that are identical in them due to their shared ancestry
- C = cost to actor; often measured in lost offspring)
signals vs. cues
- signals are evolved trait that are selected for their communicative effects (e.g. a crow gives a rally call that causes other crows to join it to attack a threat)
- cues are non-communicative environmental aspects that guide the behaviour of an individual, in a way that enhances its fitness (e.g. mosquitos use CO2 humans to detect humans)
brood parasitism (manipulation)
- many birds think that their eggs are theirs, as long as it’s in their nests
- brood parasites dump their eggs into host nests, for the host parent to waste resources to raise them
- brood parasite nestlings often kill the young of hosts to ensure more resources are directed to them
eusocial organisms
colonial, multigenerational organisms with extreme cooperative brood care (e.g. bee colonies have worker bees)
ritualization
- non-communicative behaviors transform into communicative signals, often becoming stereotyped and exaggerated for better communication
- originated from other functions
- e.g. piloerection (fluffing hair) in cats to look bigger and more threatening originated from thermoregulation
four types of communicative outcomes
- mutualistic (cooperative): the signaler and receiver benefits
- altrustic: the signaler is costed, the reciever benefits
- manipulative the signaler benefits, the reciever is costed
- spiteful: the signaler and receiver are costed
five types of communication channels
- vision
- audition
- chemical
- touch
- electrical
three aspects of ritualization
- behaviour conspicuousness: behaviour is quite visible (e.g. peacock tail size increases generationally due to sexual section)
- reduced ambiguity: behaviour is less likely to be misread
- increased separation from the original function: behaviour is often in conflict situations (e.g. threat, reproduction)
agonistic behaviour
social behaviour that involves aggression (i.e. threats) and submission (i.e. avoidance)
components of communication, and university lectures as an example
- signaler: sends the message (e.g. professor)
- channel: how a message is sent (e.g. sound (voice) and vision (slideshows)
- receiver: receives the message (e.g. students)
- noise: makes communication harder (e.g. students talking)
steps of bird song acquisition
- sensitive period: birds can hear songs in their nests
- twittering: similar to babbling like a baby
- plastic song: some correct syllables, but not fully fledged out
- structured song: successfully learned the song
communication
process in which a specialized signal produced by one individual affects the behaviour of another individual (there needs to be a response)
honeybee communication
- bees dance to communicate location about resources
- the bee tells the other bees whether to run towards or away from the Sun, and at what angle the food is situated to the Sun
examples of messages that can be communicated through signals
- recognition of social groups
- mate attraction (bringing a mate to you)
- courtship and mating
- maintaining a social bond (e.g. humans hugging)
- alarm and safety
- aggregation (communication between different species)
- agonistic encourters (i.e. fighting, submission)
- sharing information about resources
cooperation
- behaviours that have evolved, due to the benefit of the recipients
- requires that the individuals involved communicate with each other
- e.g. ants form bridges to help other ants
Belding’s ground squirrels, and Hamilton’s rule
- females are philopatric (tend to return/stay near their mothers), whereas males tend to disperse
- females do more alarm calling than males, as they are surrounded by many close relatives, in comparison to males
three categories of fitness
- direct fitness: individual’s reproductive success
- relative fitness: comparison between an individual’s reproductive success, and the average reproductive success of the population
- indirect fitness: relatives’ reproductive success
allogrooming
- social grooming, due to hygiene or appeasement (conflict resolution)
- can happen between different species (e.g. a dog and a cat sleeping together)
four “altruistic” hypotheses
- by-products benefits: acts in which both the actor and recipient benefit immediately (mutualism; not actual altruism)
- manipulation: the recipient tricks the actor into “altruistic” behaviours (the actor doesn’t consciously act altruistically; not actual altruism)
- reciprocity: acts that benefit the recipient today, with an expectation that the actor will be repaid in the future (delayed mutualism; not actual altruism)
- kin selection: aimed at close relatives, as they are genetically related to the actor
