Darwinist Nathan Lents is the author of Human Errors: A Panorama of Our Glitches, from Pointless Bones to Broken Genes, a book that purports to point out “poor design” in biology. He replies here to our criticism of his claims of poor design, specifically his claim that the maxillary sinus drainage (in the face) and the location of the testicles in the scrotum outside the body are examples of poor design. I’ve pointed out two things about his arguments:

1. His arguments are design arguments, obviously. He uses the theory of intelligent design — the theory that design is detectable in biology — to ferret out “poor design.” Whether specific organs are designed poorly or not (ID is not a theory of “perfect” design), Lents is using design theory in his work. He implicitly makes our point for us: the inference to design in biology is scientifically powerful. It helps us understand biological structure and function. In some instances, it helps us understand biological mistakes. The design inference is good science, and Lents’s entire book is based on it. 
2. His two specific examples of “poor” design — the maxillary sinus and the testicles — may in fact not be poor design at all. 

On the maxillary sinus, Lents argues that the ostium at the top of the maxillary sinus is not an overflow drain, and he points to apes who have ostia situated better for gravity drainage. Lents ironically makes a point that design scientists have been making all along: consideration of design principles leads us to a much deeper understanding of biology. Is the maxillary ostium an overflow drain? Why does drainage normally move uphill by ciliary action, rather than downhill by gravity? Why is there only one ostium in the maxillary sinus, rather than many? To what extent does the drainage of mucous depend on flux of the water component of the colloid back through the mucosa, rather than through the ostium? These are all good questions, and they are the kind of questions that lead scientists to a deeper understanding of physiology. They are, of course, design questions. Lents uses them liberally, yet he lacks the insight to see that he is practicing intelligent design science, especially when he makes “poor” design arguments. 

On testicular design, Lents declares “I’ll play ball.” His theory that testicular anatomy is “poorly” designed is likely misguided. In his post, he meanders on for several paragraphs about “optimal temperature” for sperm development, and laments hernias and testicular damage. This, he says, is poor design. I point out that a perfectly good case can be made that production of sperm in a cooler environment is adaptive, in that it maintains the sperm at a lower metabolic rate until they are needed. Who is right? It remains to be seen. We can, and should, explore the design principles inherent to reproductive physiology. Note the contrast between the usefulness of the design inference in exploring this physiology, and the irrelevance of Darwinian speculation about testicular evolution. The design inference leads to deep insight about biological function. Darwinian speculation is storytelling, of no real value to medical scientists. Just-so stories, even if true, are scientifically empty. 

In all of his “poor” design arguments, Lents inadvertently embraces the design inference. These questions about maxillary sinus anatomy and sperm development and temperature and the downsides and upsides of male reproductive anatomy are good and interesting questions — they are a good way of doing science. They are design science. They only arise when we ask: Why would this organ be designed like this? Sometimes, a deep look into the science provides us with elegant answers. The genetic code, the immune system, neural networks, and the eye are only a few of the countless examples of the power of the design inference in scientific inquiry. 

I challenge Lents: Try to understand biological function without inference to purpose and design. It has been observed that every biological function has two explanations: a proximate explanation (its function) and an evolutionary explanation (how it came about). Proximate explanations depend critically on biological purposes, which can only be explored by inference to design. Evolutionary explanations merely provide narrative gloss, and are of little if any value to scientific understanding of biological processes. 

Yet Lents is right, in an important sense. Undoubtedly, biology is replete with “poor” design. Nature is imperfect. There’s a lot of amazingly good design too. And intelligent design science, which Lents uses to make his arguments, is the most effective way to explore it.

Photo credit: KeithJJ, via Pixabay.