Muscle is one of the most fundamental of animal tissues. It is muscles that animate our bodies — allowing us to move, stand upright, breathe, and even speak. Muscles are precisely the sort of thing that we might expect a designer of embodied intelligent beings to produce.

Here, I will address an objection to irreducible complexity I’ve encountered that attempts to handwave the argument away as though I were missing something obvious. This is, in my judgment, one of the weakest objections to irreducible complexity, though it persists as a popular one — even among experts. It is therefore worth commenting on. I will use as case examples two responses to recent articles of mine.

As in the case of so many physiological processes, the male erection and ejaculation reflex requires multiple processes to function in unison to achieve a higher-level objective — in this instance, depositing seminal fluid, containing millions of sperm cells, in the female vaginal cavity.

An important requirement of life is a means of minimally accurate self-replication. Biologist Jack Szostak explains that “In order for RNA to have emerged as the genetic polymer that enabled protocells to evolve in a Darwinian manner, the process of RNA replication must have been accurate enough to allow for the transmission of useful information from generation to generation, indefinitely.”

The intricacies of vertebrate blood clotting represent a significant challenge to evolutionary mechanisms. The process of clot formation is itself irreducibly complex and must also emerge simultaneously with a mechanism to prevent excessive clotting and to confine the clot to the site of injury. From a neo-Darwinian perspective, it is difficult to envision such a system emerging one step at a time without passing through maladaptive intermediate stages.

It is difficult to imagine a more profound testimony to design than the delivery of a fully developed baby that, only nine months ago, was a single cell. Few biological phenomena are as gripping and awe-inspiring as the process of reproduction and the development of a baby in utero. The signature of design here is unmistakable, for so much of the process — from conception to delivery — depends on foresight and planning.

One of the most incredible features of cellular life is the capability of self-replication. Bacterial cells divide by a process known as binary fission — an amazing feat of engineering, requiring a myriad of different proteins. Several features of bacterial cell division exhibit irreducible complexity. This represents a fundamental challenge to evolutionary explanations of its origins. Here, I will focus only on the severing and re-synthesis of the bacterial cell wall.

Human reproduction is perhaps the quintessential example of teleology in biology. The process by which a fertilized egg develops into an infant over the space of nine months reveals exquisite engineering and ingenious design. Before this intricate process can even begin, there is a need for a sperm cell to fuse with an ovum — each carrying, in the case of humans, 23 chromosomes. This incredible feat bears the unmistakable hallmarks of conscious intent and foresight.