Is the Male Reproductive System Poorly Designed?

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Evolution’s “poor design” claim

by Jerry Bergman

One of the latest proofs of human evolution is the poor design claim, namely that an intelligent Creator would not design some human body part in a certain way. An example is the human male reproductive system, which Rowe listed as number four in his list of the top 10 design flaws in the human body. The human male reproductive system poor design claim focuses on the view that “if testicles were designed”, then why didn’t God “protect them better. Couldn’t the Designer have put them inside the body, or encased them in bone” like the brain which is surrounded by a hard skull?

Concluding that a body structure is poorly designed, as Oxford University Ph.D. Professor Hafer claims, instead of asking why the existing design exists, is a science stopper. The ‘why’ question motivates research into the reasons for the design. When this approach was applied to the human appendix, the tonsils, the backward retina, and the many putative other examples of supposed poor design, good reasons for the existing designs were found in all cases. The same is true of the male reproductive system.

Hafer explained that when she was looking for new approaches to refute Intelligent Design, she knew she “had a winner when … in the middle of an Anatomy and Physiology lecture” she concluded that the male reproduction system “is a great first argument against ID”. She believed that she also had a good “political-style argument” against ID. Her main argument is that because male testicles are outside of the body, they are prone to injury. She adds that in many animals, including cold-blooded reptiles, they are located inside the body where they are fully protected.

The reasons for the design

Male testicles exist outside of the body in humans and most mammals for several important reasons, including effective regulation of scrotal temperature for optimal spermatogenesis development. Another reason is to keep sperm relatively inactive until they enter the warm confines of the female reproductive system. Even just a few degrees above the optimal temperature is detrimental to both sperm production, specifically in the later stages of spermatogenesis, and sperm maturation.

A low ambient temperature is essential for normal spermatogenesis in humans and most mammals because the enzymes required for the process are denatured if their temperature is not finely regulated. One study in mice found temperatures of 37˚C or higher caused “a significant reduction in the percentage of motile sperm”, producing an increase in the number of spermatozoa with plasma membrane damage. The mammal exceptions include monotremes, mammals that lay eggs instead of giving birth to live young, and have intra-abdominal testes. Also, some placental mammals, such as insectivores (shrews, hedgehogs, and moles), plus elephants and hippopotamuses, all have intra-abdominal testicles. One factor is externalized testes are found only in certain mammals whose lifestyle involves jumping, leaping, or galloping. In large animals with this lifestyle this behaviour would be expected to put great pressure on the testicles and even expel their contents by creating concussive hydrostatic rises in peritoneal pressure…

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image credit: Olga Guryanova