Biological Science: Kin Selection and Altruism

Kin Selection Lecture Overview

• Learning Outcomes:

  • Define altruism with examples.

  • Differentiate between cooperation, reciprocal altruism, and kin selection.

  • Identify conditions aiding the evolution of kin selection, referencing Hamilton’s rule.

  • Calculate coefficient of relatedness among individuals.

Understanding Altruism

• Definition:

  • Altruism involves actions that benefit another individual’s reproductive success at a cost to one's own survival/reproduction.

• Examples:

  • Meerkats and bee-eaters exhibiting altruistic behaviors.

Models of Altruistic Behavior

• Types of Altruism:

  • Cooperation: Mutual benefit interactions (e.g., symbiotic relationships).

  • Reciprocal Altruism: Acts exchanged between non-related individuals (e.g., grooming among vervet monkeys, blood donation among vampire bats).

• Kin Selection: Favoring traits that benefit relatives (e.g., bee-eaters helping in parental nests to increase indirect fitness).

Inclusive Fitness

• Definition: Combination of direct and indirect fitness derived from reproducing offspring (direct) and assisting relatives (indirect).

• Calculating Relatedness:

  • Relatedness coefficient (r) measures genetic similarity (e.g., siblings have r = 0.5).

Hamilton’s Rule for Altruism

• Formula: Br > C

  • B = Benefit to recipient.

  • r = Relatedness between altruist and recipient.

  • C = Cost to the altruist.

• Application: High benefit and low cost favor altruistic behavior (e.g., saving siblings).

Examples in Nature

• Sexy Son Hypothesis:

  • Selection for attractive mates to produce attractive offspring.

• Inclusive Fitness: Males contributing to the survival of their kin increase their genetic propagation, as seen in turkey mating displays among brothers.

• Recognition in Kin Selection: Ability to discern related individuals enhances cooperative behaviors in species like the Side-Blotched lizard.

Conclusion on Altruism Strategies

• Individuals behave altruistically primarily for their own genetic advantage, focusing on inclusive fitness.

• Cooperation and altruism occur when benefits exceed corresponding costs.

• Key Takeaway: Individual benefits guide behaviors; altruism serves genetic self-interest even in forms that seem self-sacrificial.

Next Topics

• Discussion on microevolution and its significance in evolutionary biology.