The Evolution of Helpful Behavior and Altruism

Mutualism Team of male lions, 2-3 members Lazuli buntings Hunt together Share access to females pretty equally Going alone would not be as successful (cost-benefit) Lazuli buntings Dominant, bright colored males tolerate dull subordinate males in neighboring territories Good territory for sharing of females

Reciprocity Initial helpful action leads to a benefit later on when that helpful action is returned Sentinel theory Personal safety theory Supported by more observations than sentinel

Reciprocity in flycatchers Birds observe their neighbors being “attacked” by stuffed hawks on both sides They help mob the hawk attacking the neighbors that helped them in an earlier experiment Detect attack, realize implications of attack, recognize neighbors that helped them earlier, decide to help those neighbors now, over the neighbors that did not provide help to them

Reciprocity in primates Sharing ability of the actor, when he was paired with a trained altruist, who always pulled for him, and a “defector” who pulled randomly

Problems with reciprocity Defectors take a free ride Don’t repay helpers Prisoner’s dilemma Multiple interactions hypothesis Multiple interactions complicate Silence=altruism, always better for the other person (cooperate) Confession=selfish, always better for self (unless both confess) (defect)

Altruism and Indirect Selection Theory relies on the passing on of ones alleles, which are shared with close relatives Relatedness is key, as siblings>cousins>second cousins in terms of genetic similarity Relatives fight each other less often, cooperate more often

DQ If an altruistic act increases the genetic success of the altruist, then in what sense is altruism actually selfish? Words like “altrusim” and “selfishness” carry implications about motivation and intent…why might the everyday usage of these words get us in trouble when we hear them in an evolutionary context? If an individual inadvertently helped another at a cost of his own reproductive success, would such an action be considered altruistic in the evolutionary sense? In the ultimate sense, the intent doesn’t matter at all

Relatedness dependent cooperation Mothers brood eggs in the nest, males guard against intruders

Altruism in Belding’s ground squirrel Alarm call to alert others of predator Signaler does get killed more often Altruism as direct and indirect selection: Females call more often when their offspring and/or nondescendent relatives are neighbors