Altruism A Simulated Investigation

1. COM SCI 194 Honors Research Fall 2007 ~ Spring 2008 Alexander Liu and Eric Chang Professor Amit Sahai Altruism A Simulated Investigation

2. Why Study Altruism? • First, a definition • Existence in species both animal and human • Impact on human society and culture • Above all, it’s exciting!

3. Previous Works • Haystack model • The evolution of altruism: Game theory …Fletcher & Zwick • Usage of A-life to support evolutionary biology theories • Avida

4. Mathematical Models • Price’s Equation “In other words, for b>a there may be a positive contribution to the average altruism as a result of a group growing due to its high number of altruists and this growth can offset in-group losses, especially if the variance of the in-group altruism is low. In order for this effect to be significant, there must be a spread in the average altruism of the groups.” • Hamilton’s Rule • r = the genetic relatedness • B = the additional reproductive benefit • C = the reproductive cost to the individual of performing the act.

5. Our Scope • Not about morality or conscientious intent… • Origins and reason for persistence • How does a gene that decreases the fitness of the individual get passed on through generations?

6. Approach • Advantages of virtual simulation • Direct and fast • Building our framework: eden.java • Design parameters and requirements • Limitations and caveats

7. Our Own Little eden (.java) • Overall description • The world environment • Food availability and resolution • Reproduction • Genetic variance through succeeding generations

8. Base Experiment • First in our “main line” of experiments • Either completely altruistic or completely selfish • Random movement • Results • Why?

9. Variable Levels • Altruism levels allowed to vary in increments of 0.1 between 0.0 and 1.0

10. Modifications • Food sharing between parent and child organism • Same trait governs two behaviors

11. Genes, not Numbers • Instead of a sliding scale, behavior is governed by a gene-set • Genes have a chance to turn on or off

12. Extension and Comparison • Problems with a small gene-set • Effect of increasing the gene-set • Comparison with the previous results

13. Back to the Numbers • Altruism levels allowed to vary between 0.00 and 1.00 in increments of 0.01

14. Sexually Determined Altruism • Regardless of starting conditions, the distribution always converges to a selfish result

15. Selective Altruism • In previous experiments, there is no clear advantage to being altruistic • Test Condition: altruistic organisms only share with similarly altruistic neighbors Mutation rate: 20% chance of +- 0.1 Selective Range: Shares with altruists +- 0.05 range

16. Altruism vs. Selfishness Revisited • Hording Behavior Observed • Population Distribution Snapshot at Equilibrium: Pure Altruistic Pure Selfish • 1.0: 0 72 • 0.9: 0 86 • 0.8: 4 79 • 0.7: 2 57 • 0.6: 15 67 • 0.5: 32 41 • 0.4: 59 10 • 0.3: 87 0 • 0.2: 65 1 • 0.1: 97 0 • Equilibrium eventually breaks. • Altruists exhibit much more robustness and consistent rebounding

17. Conclusions • Contingent upon several conditions • Conditional altruism • Relatedness and locality • Beginnings- parent/child interaction • Persistence • Altruists do benefit (each other) • Price Equation

18. Distinctions • Differences between altruism in animal species and in human society • The importance of a persistent culture • And transmission of cultural elements • Genetic basis versus expression

19. And… • Final thoughts • A big thank you • Questions?