Sexyloop: Self-Reproduction, Evolution and Sex in Cellular Automata

We created a simple evolutionary system, sexyloop, on a deterministic ten-state five-neighbour cellular automaton (CA) where self-reproducing loops have the capability of sex. With this ability, the loops are capable of transferring genetic material into other loops. This work was based on Sayama´s evoloop which was transformed by adding a new state and new rules. The evoloop model showed an emergent evolutionary process only due to an adaptation of the loops to interaction in the environment; and after a certain time, all the individuals capable of self-reproduction belonged to the smallest species 4 which reproduced the fastest. We created two different models of self-reproducing loops with sex, sexyloop M1 and M2, in order to study the possibility of sex in self-reproducing automata and to assess the impact of sex on the evolutionary process via comparing between the evoloop and the sexyloop variants. In the sexyloop M1 and M2, the diversity of the whole population was different from that found in the evoloop and the evolutionary process was quite different too. The sexyloops also created smaller and bigger species than the evoloops, and exhibited greater diversity and faster evolution than their non-sexual counterparts. The most interesting model was the sexyloop M2 whose evolutionary dynamics had a very different longterm behaviour than the evoloop and sexyloop M1. The most surprising and intriguing phenomenon in the sexyloop M2 was that the evolutionary process was selecting quickly a bigger species than in the evoloop and sexyloop M1: the species 5. In fact, the individuals from this species needed more time to reproduce than those from the species 4. So it appears that in the sexyloop M2, the fittest individual was not one that could reproduce the fastest but surely one that reproduced fast and which was more adapted to propagate in an environment where sex with individuals of the same and other types could occur. These results give the first examples in ce- llular automata of evolution in a population of self-replicators where sex plays an important role