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« on: June 05, 2008, 08:39:10 AM »
Just wanted to share some of my first experiences with the community, so here it goes.
My intention was to get an evo sim going with predator and prey coevolving in a predator prey cycle without external interference like constant energy (day night) or polulation caps (max veggies, costX). I started with just a veggie (runaways) and set the physics and cost. I adjusted the nrg influx so that the veggie population barely survived the first reproduction cycle, figuring that if the veggies would get more than that they swould have conquered the world already. Next I added the predator(animalis minimalis) in a 1:10 ratio. The sim busted for several repeatedly for several reasons:
1) no variance in population: predators and all prey each started all having the same parameter values: age, energy and body of each individual in the population were the same. This meant that every so much cycles the prey would reproduce all at once, peaking its population. I tried to solve this by adding some randomness to the prey reproductive gene, but that wouldn't help me at start up. Secondly the predator would reproduce sucessfully but its offspring would not survive food competition. The original predator population grew old and died without leaving sustainable offspring. A decent age build up would have prevented that
2) predator and prey were both dumped with in an environment. They hadn't coevolved with each other in this environment. Basically I dumped an alligator and a penguin in the desert and was waiting for predator prey cycle. What are the chances of that happening?
So I gave up and added caps: CostX for the predator, constant system energy for the prey. A minimum veggie population above the starting population increasing by 1 every cycle, to get a more even prey population build up, adding predators manually for the same reason. CostX screwed up my minimal energy balance of prey, so I upped the nrg/turn. This resulted in the working sim attached
The first muation to catch on was collision avoidance: dont up the speed for distance <6, which makes sense in the elastic collision sim. At first I thought the gene was degrading, so I reran with both the original and the mutation. The mutation would replace the original every time. Another was conditional rotation: rotate small angles with targets in sight, otherwise large. A third was to travel if no food was available as opposed to waiting and starving. All clear energy aquiring or saving mechanisms. I have to admit after that the genes have become too obscure for me to identify improvements beyond that.
One mutation I was expecting but which did not appear for considerable amount of time was higher survival of offspring. Amimalis give 10% to offspring, which leads to high infant mortality (8-9 average offspring) in the environment. A mutation on this point could take over quick.
I have observed a number of things in the sim:
1) Since animalis genes are all functional neutral or positive mutations usually start within randomness or at the end of a gene. A future experiment of mine is to duplicate all genes and re-run. Is the species with all genes double stronger (better resiliance when mutating) or weaker (killer breakdowns occur more often)?
2) once on a while the number of subspecies collapses. Population of predators noramally ranges beteen 180 and 220, so I don't see mass extinction as the cause. I think it is a more adapted subspecies taking over at the expense of population diversity. I wonder what impact sexual reproduction would have on stability of species diversity.
3) best mutations don't occur first. Open door of course, since mutations are random, but I was waiting for infant mortality to come down by an improvement in the reproduction gene, and all kinds of things happened, but not that.
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