Extra credit: Scientists working on dog size variation research discovered a polymorphism aseociated with ail dog treeds sharing which size phenotype? small breeds large breeds they were unable to find an association between a single nucleotide polymorphisn and any specific sue claty medium breed neutral evolution is the mechanism most likely to have maintained left- handedness in humans despite is sigrifant fitres com negative freyusncy-dependent selection linkage diseguilibrium stabilizang sciection positive trequency-dependent selection.