King and Wilson (1) inferred from this   and other evidence that structural gene evolution and morphological evolution   may proceed at independent rates. Some biologists, however, have been   reluctant to agree with King and Wilson that there really is a contrast   between the morphological and biochemical results of evaluating the   difference between chimpanzee and human (3). Although these biologists are   aware of the quantitative and objective nature of the biochemical comparisons,   they are also aware that the chimpanzee-human, morphological difference has   never been compared quantitatively with the morphological differences   existing among other species. This lack of confidence in the morphologists'   judgment that the chimpanzee-human difference is as big as that among the   families of other animals is illustrated by Merrell (3). He stated, in   essence, that if a nonmammalian creature were to classify animals on the   basis of morphology, the chimpanzee-human difference might seem very small.   In particular, he suggested that the chimpanzee-human difference might be no   larger than that between two sibling species of frog (4).

King和Wilson（1）基于这一点和其它证据推断，结构基因进化和形态进化可能以独立的速率进行。然而，一些生物学家不同意King和Wilson的观点，即在评估黑猩猩和人类之间差异中，形态学和生物化学结果之间确实存在着一种鲜明对比（3）。尽管这些生物学家知道生物化学的比较较为量化和相对客观的本质，但两个物种从未在形态进行过量化差异比较，就像其他物种之间存在的形态差异比较。Merrell（3）证明，黑猩猩与人类的差异如果参照其它动物类群，已经达到了科级水平，致使把它们作为两个同属物种缺乏信心。他说，从本质上讲，如果一个非哺乳动物的生物要根据形态学对动物进行分类，那么黑猩猩与人类的区别可能看起来很小。特别是，他认为黑猩猩与人类的差异可能不大于两个蛙类姊妹种之间的差异（4）。