Evolutionists claim what is called atavism as evidence for universal common descent. However, the designation often presupposes universal common descent. For example, in our investigation of it, see previous articles, we have seen several cases where these features are more likely than not simply birth defects or genetic defects. Furthermore, in cases where they may actually qualify as atavisms only qualify as evidence for universal common descent if it is assumed.
A classic example of this is the so-called human tail. Evolutionists will commonly claim that the extension of the spinal column in the early stages of fetal development is atavistic. They do so on the assumption that human beings descended from animals with tails such as monkeys. This claim ignores the fact that this fetal feature is simply part of the development process. Sometimes something goes wrong during fetal development, resulting in a tail-like structure. However, this is not a functioning tail, but simply an extra growth that may or may not contain vertebrae. Seeing how this can happen based simply on the process of fetal development is quite easy to see.
Another classic example is the tendency of evolutionists to categorize excessive amounts of hair in humans as atavistic. They base this on the presupposition that we evolved from animals such as apes which have significant amounts of body hair. This argument would make more sense if humans had no body hair, but we do. Consequently, such cases are just an example of how extreme the presence of hair can get in human beings. It does not qualify as atavistic let alone evidence for universal common descent.
Ultimately the problem with regard to the label of atavism is that it is often applied when it fits universal common descent, but it is not applied when it clearly goes against it. A good example of this is the fact that the label is applied when Guinea pigs have five toes, but not when human beings have six fingers. Ultimately, it is a case where the label atavism is applied because it seems to fit universal common descent, and then it is used as evidence for universal common descent. Consequently, ultimately this is circular reasoning.
While there is some evidence of actual atavisms within some of the creative kinds of animals. Most examples given by evolutionists are birth defects, genetic defects, programmed changes in some species in response to environmental conditions, and existing variety within a species. Meanwhile, whether or not certain forms qualify as atavism is based entirely on the presupposition of universal common descent, making the argument circular reasoning. Finally, the Biblical model of genetic deterioration explains both how these traits can disappear and even reappear the way they often do.
