Source: Original cartoon by Alex Martin

Without social pressure, most people give little thought to male circumcision. This simple surgical procedure removes the foreskin, a hood of skin covering the head of the resting (flaccid) penis. But questions commonly arise soon after a baby boy is born, when a physician may offer or recommend circumcision. This is what my wife and I experienced with both of our sons, and we decided against circumcision.

Source: Wikimedia Commons; Author: MrArifnajafov. File licensed under the Creative Commons Attribution-Share Alike 1.0 Generic license.

However, when about 10 years old, one son seemingly had difficulty rolling back his foreskin. Our pediatrician warned us that this could lead to phimosis — a medical condition in which the foreskin chokes the penis — and strongly recommended circumcision. Anxiously, we decided to wait and see, and the apparent problem eventually disappeared. In fact, background research for this post made it clear that the foreskin cannot normally be rolled back in young boys and may not become fully retractable until late or even early adulthood. Widespread failure to distinguish between true phimosis and non-retraction during normal development frequently leads to misdiagnosis.

Source: Composite image based on two figures provide by Kayaba et al. (1996).

Fore-runners of foreskins

With any biological issue, my zoological training locks in and impels me to explore its evolutionary history. But soft tissues are rarely preserved in the fossil record, so we can expect little help from that quarter regarding the foreskin. We can, however, learn a great deal by comparing living forms, taking the entire penis as a starting point.

Among vertebrates, the more primitive aquatic forms — fish and amphibians — generally lack any kind of intromittent organ (the technical name for a penis) because fertilization is typically external. But during the major transition from aquatic life that accompanied the evolution of land vertebrates — reptiles, birds, and mammals — internal fertilization became essential. In fact, this shift did not make a penis obligatory, as it is lacking in most birds and an early-diverging lizard-like reptile, the tuatara (renowned for the third eye on the crown of its head). In these species, to transfer semen the male simply needs to press his rear end (cloaca) against that of the female.

Source: Adapted from a figure in Martin (1990)

But most land vertebrates possess a penis, and in an evolutionary analysis published in 2002, Diane Kelly concluded that it probably evolved independently at least three times separately: once in the common ancestor of crocodiles and tortoises, once in the ancestor of snakes and lizards (which have a double penis), and once in ancestral mammals.

Source: Author’s diagram based on a basic tree from Kelly (2002).

A penis is present in all living mammals, so the beginnings of the foreskin may date back to the origin of mammals, around 200 million years ago. Certainly, as all living placental mammals have a well-developed foreskin, this feature was established before 100 million years ago. In all placental mammals, the foreskin (prepuce) is a retractable, double-layered membrane covering the head of the flaccid penis, providing protection and lubrication. But the foreskin is also equipped with many touch-sensitive nerve-endings. So circumcision removes a structure that has been finely adapted over a truly extensive evolutionary history.

History of human circumcision

Circumcision doubtless originated as a ritual, probably in a religious context. Today, foreskin removal is generally performed soon after birth, but it is widely accepted that it started out as a coming-of-age rite performed when boys reached .

Although ritual circumcision presumably dates back tens of thousands of years, archaeologists have found no concrete evidence for such early occurrence. It has been claimed that some penis depictions in European cave art (between 38,000 and 10,000 years ago) include examples of circumcision. But the penis is typically erect and the state of the shaft is unclear. Moreover, such depictions appear to include cases where the penis was not circumcised, so the practice was evidently not universal.

The oldest known evidence clearly showing circumcision comes from Ancient Egypt, with documentation from around 4,500 years ago both in a tomb mural and in a written account. In these and subsequent cases, circumcision was performed not soon after birth, but on adolescent boys.

In the modern world, circumcision is linked to many different religions. It has diverse origins but shares a single source for the Abrahamic faiths of Judaism, Christianity, and Islam (listed in the order of their founding). In Genesis 17:11 (World English Bible) God says to the patriarch Abraham: “You shall be circumcised in the flesh of your foreskin. It will be a token of the covenant between me and you.” Complying with Abraham’s covenant, a Judaic circumcision is customarily performed on the eighth day of life. This, then, clearly marks an ancient switch to circumcising boys soon after birth rather than at puberty.

Source: Wikimedia Commons; Author: AHC300 & Bech, April 30, 2017. File licensed under the Creative Commons Attribution-Share Alike 4.0 International license.

Reflecting differences between religious faiths and the declining importance of religion in many regions, rates of circumcision vary widely around the world, from 80-100 percent in North Africa, the Middle East, the Caucasus, and Southeast Asia to near zero in parts of South and Central America, Europe, and Asia. A notable difference is seen in North America, where strikingly high rates of around 80 percent in the U.S. contrast with moderate rates of 40-50 percent in Canada. Yet, a century ago circumcision rates in the U.S. were around 50 percent, as in Canada. Today’s difference is, however, not attributable to religion but to medical practice: Surprisingly, the most animated controversy surrounding circumcision in the modern world hinges not on religion, but on acceptance or rejection of medical justifications.

Source: Adapted from a figure provided by Cox & Morris (2012).

In fact, almost-hysterical opposition to initially triggered active medical advocacy of circumcision. (See my post: Masturbation: Self-Abuse or Biological Necessity? November 16, 2017.) Beginning in the late 1800s, circumcision of newborn boys became routine in the U.S. and Britain at least partly because it was believed to reduce the incidence of that “evil habit." Although strictures against male masturbation began to wane significantly at the dawn of the 20th century, their legacy may persist subliminally in medical advocacy of circumcision.

Over the past 80 years, many publications have reported the health benefits of circumcision. Initially, a major issue was protection of men against infection with syphilis, eventually eclipsed by the threat of infection with the HIV virus and consequent development of AIDS. Circumcised men also reportedly have a lower risk of contracting genital herpes and cancer-provoking human papillomavirus (HPV).

In addition to reducing the risks of sexually transmitted diseases, various other health benefits for men have been noted, including a reduced incidence of urinary tract infections. Furthermore, research has indicated that circumcision reduces infection risks for women during as well, notably for HPV, bacterial vaginosis, and trichomoniasis.

For decades, physicians in Australia, Britain, and the U.S. have engaged in vigorous discussion about the advantages and disadvantages of circumcision. In 2014, however, for the first time in its history, the Centers for Disease Control (CDC) issued explicit guidelines strongly endorsing early-life circumcision as a health measure. This did not go unchallenged. In 2015, for instance, Brian Earp issued a well-argued critique, particularly emphasizing the of circumcising young boys before the age of informed consent. The debate continues.

What about women?

This discussion has been deliberately confined to male circumcision, although there is a notorious female counterpart. I will devote a separate post to female genital mutilation. Several authors have argued that it is confusing and counterproductive to consider male and female interventions together. Effects of female genital mutilation, which is far less common than male circumcision, are undeniably more dramatic and differ crucially in certain ways—for instance, no health benefits have ever been proposed. It may hence be acceptable to allow male circumcision while banning female mutilation.