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

Abstract

Abstract. 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 cellular automata of evolution in a population of self-replicators where sex plays an important role.

Dude, where is my sex gene? — Persistence of sex over evolutionary time in cellular automata

“…Finally, the umbilical cord dissolver moved back into the attacker arm to retract it and a sheath '2' was created in its previous location. At the same time, the signal blocker, the detection sheath and the blocker dissolver disappear (see [6] for more details).…”

“…When the tip of a loop's arm hits another loop on its sides or the corners, a dissolving state appears eventually deleting the "attacked" loop and the attacker's arm. Like in [6], we mean by "attacker" the loop that will transfer its genetic material into another loop (the "attacked" loop). The use of the term "attacker" in this paper is due to the fact that in our scenario, the donor transmitting heritable information sexually is generally at an evolutionary advantage compared to the recipient as the latter generally loses some part of its genome in such interactions.…”

“…Models of selfreproduction have been described in CAs [7,10,11] and Darwinian evolution has been exhibited in populations of self-reproducing loops [6,12,13]. In the sexyloop [6], we managed to allow the transfer of genes from a loop into another one using a simple mechanism with a minimum number of new states, using a mechanism similar to bacterial conjugation [2,3].…”

“…Here we understand 'sex' as the transfer of heritable genetic material between individuals [2,3] (see also discussion in [6]). 1 In Artificial Life the study of self-reproduction goes back to the work of von Neumann on self-reproducing automata implemented in cellular automata [7], but few evolutionary models have supported any bottom-up autonomous capacity for sex (exceptions include Tierra [8] in assembly code programs, and [6] in Cellular Automata; see also Vitányi [9]), and prior to the work presented here no such models, to our knowledge, have investigated evolution and persistence of sexual mechanisms. Such a study takes us beyond the examples of 'sex as-we-know-it' in organic biological systems [2][3][4] toward a more general understanding of 'sex as-it-could-be' in other instantiations of living systems.…”

“…In order to investigate the persistence of sex in a population of self-reproducing loops, here we introduce a new simple evolutionary system, based on the sexyloop [6], where sex is only performed using a specific gene. In the sexyloop, a loop was able to transfer its genetic material into another one.…”