Playing Evolution Games in the Classroom

1. Playing Evolution Games in the Classroom Colin Garvey GK-12 Fellow

2. Why don’t lions eat lions? • Lions compete with other animals for space on the savanna, but they surely compete most with other lions – overlap of needs is highest. • If individual selfishness is the overriding strategy, why don’t conspecifics overwhelmingly target one another for destruction? • Cannibalism does happen but why isn’t it the norm?

3. The central problem of evolution • Individual organisms’ needs overlap most with others of their own species • How does cooperation evolve in a cut-throat environment of selfish individuals? • Altruism is the “central problem” for modern evolutionary theory • It is locally disadvantageous, so how can it evolve in a system wherein each system change must be more fit (adaptive) than before

4. Modeling the real world • How can selfish gene theory explain the altruistic “gloved fist of nature”? • Economic cost/benefit analysis in terms of individual energy expenditure (over time) • Turns out that for A to kill B actually helps their mutual enemy C, who benefits by losing a potential threat free of energetic cost • The conditions of social life amongst selfish individuals can still lead to the evolution of altruistic behavior and the formation of groups

5. Strategies for living in the real world • Consider an idealized account of an interaction between two organisms of the same species, X • They are in competition for some resource, R • In their encounter, they have behavioral options: • Fight or Flight reactions are modeled as • Hawk & Dove strategies • The dynamics of these two idealized strategies can tell us something about the evolution of behavior

6. Get that paper, son

7. Hawk

8. Hawk vs Hawk • Brutal battle leaves one hawk triumphant, and one poor hawk gravely injured • Winner = 50 points • Loser = - 100 points

9. Dove

10. Dove vs Dove • Lots of posturing, feinting, stare-downs • Eventually, single winner emerges with 50 pts • Loss of time, but no one physically hurt • Thus both players lose 10 points • Winner = (50 – 10) = 40 • Loser = -10

11. Hawk vs Dove / Dove vs Hawk • Hawks always win because • Doves quit immediately, avoiding injury and loss of time • Winner = Hawk = 50 points • Loser = Dove = 0 points

12. HOW TO PLAY THE GAME

13. Fight! Let’s

14. Average Payoff • The average payoff for any player depends on the strategies of other players • What is the average payoff for a population of • All hawks? • All doves? • 50/50 mix?

15. The Payoff Matrix

16. Evolutionary Stable Strategies • Imagine if cach individual can play either Hawk or Dove each time • Simple pattern-based strategies will be outwitted • An important question is then if one can do better than random by playing some optimal combination of Hawk and Dove strategies • The optimal ratio of hawk/dove-ishnessdepends on the payoff and thus on (environmental) initial conditions

17. Fight!

18. Conclusions • Evolution in Action • Cost/benefit Analysis • Optimization of Goal Oriented Behavior (GOB) Future Directions • Computer Simulations • Incorporate an Understanding of Heredity • Family Trees • Exploring “Relatedness” (in a broader context)