An error sometimes made by beginning biology students is called the "Adaptationist Fallacy" wherin a trait observed in a population is automatically presumed to be the most beneficial phenotype for that species/population. Why is this presumption not always correct? Describe a scenario where the adaptationist fallacy is incorrect.

The Adaptationist Fallacy can prove very costly to biologist who are assuming it wrong according to the function in the environment. Let us have an example of the phenotype of wheat diploid breed that produces non-bearded grains variety, but we cannot assume it as a beneficial phenotype without further extensive research. After research, we came to know that there is also a major hexaploid bearded variety, that produces more number of grains. That's how, the Adaptationist Fallacy may prove fatal if we have assumed diploid as a major beneficial phenotype.