 To see why a lack of replication does not prevent evolution by natural selection from occurring, suppose a population of entities exists with different sizes, as presented in  Figure 3(a),  in which there is selection for larger entities. We assume that the entities reproduce asexually in discrete generations and that there is no environmental variation. At the parental generation, there are two types of individuals, with respective sizes of \(\frac{3}{4}\) and 1. Due to the selection for size, entities of size \(\frac{3}{4}\) produce 3 offspring while entities of size 1 produce 4 offspring. Suppose now that there is a positive heritability, as defined above, so that, on average, offspring resemble more their parent than they resemble other entities of the parental generation, as displayed on  Figure 3(a),  but only slightly so (\(h^2 = 0.2\)). After one generation, although there is no high-fidelity replication, the average size of the population has changed due to the effect of natural selection. This simple example demonstrates quite straightforwardly that replication is not required for evolution by natural selection to occur.