We have seen that mutation, along with differential survival and reproduction, is sufficient to cause increasing fitness, increasing diversity, and a simple form of speciation. This model is not meant to be realistic; evolution in natural systems is much more complicated than this. Rather, it is meant to be a “sufficiency theorem”; that is, a demonstration that the features of the model are sufficient to produce the behavior we are trying to explain.
Logically, this “theorem” doesn’t prove that evolution in nature is caused by these mechanisms alone. But since these mechanisms do appear, in many forms, in biological systems, it is reasonable to think that they at least contribute to natural evolution.
Likewise, the model does not prove that these mechanisms always cause evolution. But the results we see here turn out to be robust: in almost any model that includes these features — imperfect replicators, variability, and differential reproduction — evolution happens.
I hope this observation helps to demystify evolution. When we look at natural systems, evolution seems complicated. And because we primarily see the results of evolution, with only glimpses of the process, it can be hard to imagine and hard to believe.
But in simulation, we see the whole process, not just the results. And by including the minimal set of features to produce evolution — temporarily ignoring the vast complexity of biological life — we can see evolution as the surprisingly simple, inevitable idea that it is.