Read the following excerpt from an essay on evolutionary biology:
In mid-twentieth-century evolutionary biology, orthodox modern synthesis models held that phenotypic variations responding directly to environmental perturbations were non-heritable developmental noise devoid of long-term phylogenetic consequence. Challenging this strict dichotomy, embryologist Conrad Waddington subjected Drosophila pupae to severe heat shocks, observing that certain individuals developed an altered crossveinless wing structure. By selectively breeding only those flies exhibiting this induced response across twenty generations, Waddington produced a subpopulation in which the crossveinless phenotype emerged consistently without any thermal stress. While early critics dismissed this result as an impossible demonstration of Lamarckian inheritance, modern geneticists recognize that the temperature shock served to uncover cryptic, polygenic regulatory variation already present within the gene pool, which directional selection subsequently canalized into a stable developmental pathway.
Statement: In the context of the passage, the author mentions the 'twenty generations' of selective breeding primarily to provide empirical evidence that environmental stress causes direct, cumulative nucleotide mutations in the organismal genome.
Answer: Answer