2. Behavioral Evolution | Summary and Q&A

February 1, 2011
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2. Behavioral Evolution

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This video explores the application of Darwinian principles to social behavior. It discusses the concepts of individual selection, kin selection, reciprocal altruism, and the detection of cheaters. The video also highlights examples of cooperation and competition in various species, including vervet monkeys and bacteria.

Questions & Answers

Q: What is the difference between Bio 150, Bio 250, and Hum Bio 160?

There is no difference. They have the same requirements and unit. Students can choose whichever one is most convenient for them.

Q: Why have people taken this course?

Reasons vary, but some motivations include: interest in animal behavior, substituting it for another class, knowing a TA, wanting an interdisciplinary perspective, and personal connections or experiences related to human behavior.

Q: How can behavior be determined by the right tools and logic?

By analyzing behaviors through the lens of evolutionary principles, researchers can determine factors such as likelihood of cheating, levels of aggression, parenting skills, and life expectancy differences. This logical approach helps understand the optimization of behavior strategies.

Q: Is nature truly amazing?

Nature follows an inevitable logic in how organisms function, are built, and have evolved to solve problems. This logic is governed by principles of optimization, not just coincidental wonders. For example, giraffes need large hearts to pump blood to their long necks.

Q: How does natural selection work?

Natural selection is driven by traits that are heritable, where some versions are more adaptive than others. It is not survival of the fittest, but rather reproduction of the fittest, as the goal is to pass on copies of genes to the next generation.

Q: What is individual selection?

Individual selection is a building block of evolution that focuses on maximizing the number of copies of an organism's own genes in the next generation. This can include traits that aid reproduction and survival, such as speed or sensory systems.

Q: How does kin selection work?

Kin selection occurs when an individual foregoes its own reproductive potential to help related individuals reproduce. This is based on the idea that closely related individuals share more genes, and by aiding them, an organism indirectly increases its own gene copies in the next generation.

Q: How do animals recognize kinship?

Animals have evolved mechanisms to recognize related individuals, often through familiarity or genetic cues. This knowledge helps them determine when to cooperate with relatives and enhances their inclusive fitness.

Q: What is reciprocal altruism?

Reciprocal altruism is the third building block of social behavior, where animals cooperate with non-relatives based on the expectation of reciprocal benefits. This behavior occurs among smart, social, and long-lived animals that can remember and track interactions.

Q: How do animals detect cheaters?

Animals are vigilant in detecting cheaters within reciprocal relationships. They are more tuned to spotting cheating behavior than acts of spontaneous altruism. This vigilance helps maintain the stability of reciprocal cooperation.


In this video, the concepts of individual selection, kin selection, reciprocal altruism, and cheating detection are explored in the context of social behavior. Animals demonstrate various forms of cooperation and competition, even among non-relatives. These principles of evolution and behavior can be seen across different species, from humans to bacteria. Understanding these concepts provides insight into the optimization and evolution of social behavior.

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