EUGENE M. MCCARTHY, PHD GENETICS
Human infertility. Another observation that appears significant in connection with the theory of human origins here under consideration is that it has been well known for decades that human sperm is abnormal in comparison with that of the typical mammal. Human spermatozoa are not of one uniform type as in the vast majority of all other types of animals. Moreover, human sperm is not merely abnormal in appearance — a high percentage of human spermatozoa are actually dysfunctional. These and other facts demonstrate that human fertility is low in comparison with that of other mammals (for detailed documentation of this fact see the article
Evidence of Human Infertility). Infertility and sperm abnormalities are characteristic of hybrids. So this finding suggests that it's reasonable to suppose, at least for the sake of argument, that human origins can be traced to a hybrid cross. It is also consistent with the idea that the hybridization in question was between two rather distinct and genetically incompatible types of animals, that is, it was a distant cross.
Methodology. The chimpanzee is plausible in the role of one of the parents that crossed to produce the human race because they are generally recognized as being closest to humans in terms of their genetics (here, I use the term
chimpanzee loosely to refer to either the common chimpanzee or to the bonobo, also known as the pygmy chimpanzee; the specific roles of these two rather similar apes within the context of the theory of human origins now under consideration will be explained in a subsequent section). But then the question arises: If an ancient cross between the chimpanzee and some parental form “X” produced the first humans, then what was that parent? Does it still exist? What was it like?
