Symbiosis Promotes Fitness Improvements in the Game of Life.

Peter D Turney

doi:10.1162/artl_a_00326

Abstract

We present a computational simulation of evolving entities that includes symbiosis with shifting levels of selection. Evolution by natural selection shifts from the level of the original entities to the level of the new symbiotic entity. In the simulation, the fitness of an entity is measured by a series of one-on-one competitions in the Immigration Game, a two-player variation of Conway's Game of Life. Mutation, reproduction, and symbiosis are implemented as operations that are external to the Immigration Game. Because these operations are external to the game, we can freely manipulate the operations and observe the effects of the manipulations. The simulation is composed of four layers, each layer building on the previous layer. The first layer implements a simple form of asexual reproduction, the second layer introduces a more sophisticated form of asexual reproduction, the third layer adds sexual reproduction, and the fourth layer adds symbiosis. The experiments show that a small amount of symbiosis, added to the other layers, significantly increases the fitness of the population. We suggest that the model may provide new insights into symbiosis in biological and cultural evolution.

Highlights

There are two main definitions of symbiosis in biology, (1) symbiosis as any association and (2) symbiosis as persistent mutualism [7]
The presence of mutual benefit is theoretically interesting, which motivates the narrower definition of symbiosis as persistent mutualism
We introduce a model of symbiosis that focuses on symbiosis with shifting levels of selection

Summary

Introduction

There are two main definitions of symbiosis in biology, (1) symbiosis as any association and (2) symbiosis as persistent mutualism [7]. The first definition allows any kind of persistent contact between different species of organisms to count as symbiosis, even if the contact is pathogenic or parasitic. The second definition requires that all of the participating organisms must benefit for the persistent contact to count as symbiosis [7]. One reason for this disagreement over definitions is that there is a large gray zone of cases where it is difficult to know whether all of the participants benefit from the association. The presence of mutual benefit is theoretically interesting, which motivates the narrower definition of symbiosis as persistent mutualism

Methods

Findings

Discussion

Conclusion