Lecture 6- CooperationInclusive FitnessWe have mostly been talking about direct fitnessSelfish Genes•Natural selection results in ‘selfish’ behaviours•All that matters is the reproductive output of an individual by passing on individual genes to the next generation•Self-interest of genesoNatural selection results in increase of best replicatorsoA gene that assists other genes in replicating will not increase in number•How can helping behaviour evolve?•The idea that it is the genes that matter: passing on genetic material through generations•All that matters is reproductive output of an individualoThis is the view of evolutionIndividual genes moving to the next generation is importantoBut then how can helping behaviours possibly evolve?Why would someone sacrifice their own fitness to help another if it means they wont pass their genes on to the next generationAltruism•Behaviour that increases Reproductive Success of another individual at a costto oneself•Genes that promote self-sacrifice won’t be passed on to future generations as they are sacrificing their own reproductive outputoIf someone has this gene, they cant pass this gene on to future generations because theyare sacrificing their reproductive output•Thus, can’t evolve via natural selection...Helping•However, cooperation and helping not uncommon•How to resolve the paradox?oNepotism helping those who are related to usoIdea of helping relativesAltruism?•Helping behaviour directed to relatives is typically regarded as nepotism, not altruism•“…I help out an older woman…”oYou may think you are niceoIf they said I helped out an older women by cleaning… and it was my mother, you may be less impressed•Have an intuitive idea that helping others depends on how related we areAlarm Calling•Belding’s ground squirrels•Individuals alarm call warns others of predatoroCallers more likely to be eaten – so what do they gain? Is this altruistic?
•This seems altruistic! What is this person giving the call getting from this?Belding’s Ground Squirrels•They are getting fitness benefit through their relatives•Males disperse and leave to another area when reaching maturity, and females settle near home•You have large populations of related females in the same area•Closely related females live nearby and are protected by the male’s alarm call •Thus when an animal engages in an alarm call, it may be sacrificing itself but it is protecting its female relatives•Alarm calling more likely in:oOlder female animals that have gotten past reproductive peak so that their young female relatives are more likely to survive predationHow can we figure out when something is altruistic or nepotistic? Calculate rCoefficient of Relatedness (r)•Measure of proportion of shared genetic material in the genome oRanges from 0or = 0 would represent genetic relationship b/w unrelated individuals, and r = 1 represents identical twinso0 is the baseline for humans sharing genetic material