Hamilton’s Rule
Hamilton's rule is a principle in evolutionary biology that predicts when an organism will engage in altruistic behavior towards a relative. Formulated by the biologist W.D. Hamilton, the rule is mathematically expressed as:
r is the genetic relatedness between the altruist and the beneficiary
B is the benefit gained by the beneficiary
C is the cost incurred by the altruist
According to Hamilton's rule, altruistic behavior is favored by natural selection if the genetic relatedness multiplied by the benefit to the recipient is greater than the cost to the altruist. This rule helps explain the evolution of behaviors that appear to reduce an individual's fitness but increase the fitness of relatives who share some of their genes.
Example:
Hamilton's rule can be seen in the behavior of worker bees in a honeybee colony. Worker bees are sterile and do not reproduce themselves. Instead, they spend their lives helping the queen bee, who is their mother, to reproduce by gathering food, protecting the hive, and taking care of the queen's offspring.
Genetic Relatedness (r): Worker bees are highly related to the queen's offspring because they share 50% of their genes with their mother (the queen) and about 25% with their siblings (the other offspring of the queen).
Benefit (B): The benefit to the queen (and thus the colony) is high because the queen can produce many more offspring when she is well-supported by the worker bees. These offspring will carry on the queen's genes, including the genes that predispose workers to help.
Cost (C): The cost to the individual worker bee is significant since it forgoes its own reproduction. However, because worker bees are sterile, this cost in terms of lost direct reproductive opportunities is mitigated.
Altruistic behavior of worker bees is favored by natural selection because the high genetic relatedness (r) and the significant benefit (B) to the colony outweigh the cost (C) to the worker bees. The equation is satisfied, meaning that the genes promoting this altruistic behavior are likely to be passed on through the queen's offspring.
Author: Sanjay Adireddi
Reference Article: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3982664/
Sheiner LB, Steimer JL. Pharmacokinetic/pharmacodynamic modeling in drug development. Annu Rev Pharmacol Toxicol. 2000;40:67-95. PMCID: PMC3982664. Accessed July 31, 2024.
