The lack of access to the healthy food has caused the growth of Sebastian to slow down. In the case healthy food is provided to him, he can grow into the size he was genetically suited to. This process is known as the canalization. Canalization term is used as the measure of the ability of any given genotype to result in the same phenotype in-spite of the environmental variability.
In population genetics, directional selection is a mode of natural selection in which an extreme phenotype is favored over other phenotype, causing the allele frequency to shift over time in the direction of that phenotype
