Biologists once assumed that the phenotype of a dominant allele would always be the most common phenotype in a population. which finding led biologists to a different conclusion? the discovery that most organisms have pairs of like chromosomes and, therefore, a pair of alleles for many traits the discovery that dominant traits are adaptive and recessive traits stabilize the population the discovery of populations in which the phenotype of the recessive allele a population survive the discovery that populations undergo evolution when they are exposed to the process of natural selection