In sims with a lot of energy flying around, namely sims using corpse mode and the no decay option on nrg shots, is more advantageous to use nrg to reproduce then to grow. This is becuase reproducing increases your cross section and thus your probability of intercepting a shot to a much larger degree than growing does.
Additionlly, if using dynamic costs, a super high reproduction rate can be used as a weapon since it spikes CostX and make life harder for competitors. Even though your mortality rate will be huge, with so many more individuals, the smaller, faster reproducing bots will out compete the slower, larger guys over time in a high CostX environment since they can cover much more area and thus have a much lower probability that the entire population will go extinct due to lack of food. If you only have a few, larger, slower reproducing individuals, the chances that there will be a time where they can't see food for a while is higher, which is deadly even to larger, stronger bots in a high CostX environment. Putting yoru eggs in a thousand baskets out competes putting them in 10.
So basically, the environment today favors the evolution of fast reproducing bacteria in many sims. We could damp this down considerably if we added gestation and maturity times so that a bot could not reproduce for X cycles after birth and for Y cycles after giving birth. The longer we made these, the more it would encourage larger, more long lived bots. I favor adding these since I think most of us are interested in breeding smarter macro behaviour, not bacteria, something that is more likely to emerge for longer lived, macro organisms....
