I only had time for a small amount of work on the Web Critters project last week, however the change that I implemented had dramatic and unexpected ramifications for the state of the simulation.

On Monday and Tuesday I implemented the notion of a corpse into the simulation logic.  Instead of simply disappearing when they run out of resources, agents now leave behind a corpse object containing resources equal to the genetic material that was locked away in their tags.  (At present, offence, defence, and exchange.)  Once fully consumed, corpses are removed from the environment, just like any other resource node.

When I implemented this change I expected it to give a boost to the pure carnivores in the simulation – i.e. agents that acquire 90% or more of their nutrients from attacking other agents.  My rationale was that “meat” resources wouldn’t be quite as unstable, and could persist for a few generations after the majority of a species was predated from a location.

Startlingly, instead of seeing a spike in carnivores, every simulation that I have run since implementing corpses has seen a dramatic rise in species that are classified as omnivores (11%-89% “meat” diets), and a matching drop-off in herbivores.  The carnivore ratio is consistent with the non-corpse simulations – roughly 20%.

In lockstep with the rise of omnivores is a pronounced exaggeration of the speciation within the simulation’s population.  Previously the ratio between total agents and unique species hovered around 10:1.  With corpses introduced into the mix, the ratio has shifted to somewhere around 4:1 or 5:1; at least in simulations of less than 100,000 generations.  (I have yet to run an extended trial to see if this ratio holds.)

I am currently at a loss to explain why both of these population shifts have taken place, and require some deeper analysis tools to put together the puzzle.  One thing is for sure:  no one can claim that I’ve hardcoded any outcomes in this ALife simulation; it is truly an emergent system.

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