I worked on a similar project. One of the heritable traits I had was a quantity of energy that would be passed on to a child. A mother and father organism contr

I worked on a similar project. One of the heritable traits I had was a quantity of energy that would be passed on to a child. A mother and father organism contributed a random half of their stats to a new child and both parents deducted their caretaker energy and increased the child's energy by the same amount. I had a lot of different graphs to show me stats as the simulation continued. One thing I noticed was that after a while of this simulation "average age" started to go way up. At first, I was proud. I thought I had evolved creatures that could live indefinitely in my simulated environment. I kind of had - but it didn't work like I thought. At some point the creatures seemed to become immortal and all new creatures died off. I was monitoring "average age at death" which confirmed all the dying creatures were very young and "average generation count" which showed it stabilized midway through the simulation and then locked in place. They got to a place where new organisms died off and there were a bunch of immortal organisms running around. I finally figured out what had gone wrong. The stats, including caretaker energy, could be randomly modified by a small random value up or down whenever a child was produced. Nothing prevented caretaker energy from going negative, and indeed, that's what would happen. The simulation would work for a while while only a small number of organisms had negative caretaker energy, but eventually these guys would take over and become the whole population. They could indefinitely sustain themselves by having children, but their children (spawned by two parents who passed on negative energy) would instantly die.