Why is the penis mushroom shaped?

Does looking at mushrooms remind you of your penis?

The evolutionists claim that the mushroom-like shape of the penis evolved from the need for more vigorous thrust and the ability to clean the vagina from other men's semen.

A fully-grown mushroom may remind you of your penis.


If you have looked closely at a penis, you may have noticed its shape. It is a long cylindrical tube with a root (base), shaft, glans and foreskin (prepuce). What is the glans penis? It is a smooth head-like structure resembling a toadstool head (a mushroom). This head is extremely sensitive and enables males to have easy penetration during sex.

Although penises come in various sizes and shapes, the nature of the glans penis is nearly the same. But have you noticed the overall shape of the penis resembles a mushroom? Why is the penis shaped like a mushroom? Biologists have explained various reasons.


Anatomy of the human penis

The penis is the external reproductive organ of human males. It consists of three main parts, root, body and the cap, 'glans penis'. It is the glans penis that gives a particular mushroom-like shape to the penis.

The central part of the glans penis is cone-shaped. Besides it, it has the following structures/parts.

  • The neck separates it from the shaft (main body) of the penis.

  • Corona is the rounded border of the glans penis which starts from the base of the penis.

  • Meatus is the urethral opening from which urine and semen emit and it lies at the very tip of the penis.

  • The prepuce is the fold of skin that covers the glans penis. During circumcision, it is removed. So, circumcised men don't have any prepuce.

illustrates various parts of the human penis and other organs of the reproductive system.


The biological mushroom structure of the penis is due to the integration of these structures, and the change in the balance of these structures is responsible for vast variations in the human penis and glans penis shapes.

Do you have an average penis?

Despite all myths surrounding the size and shape of a penis, there is nothing like an average penis, as significant variations exist in sizes and shapes. In statistical terms, you are likely to have an average penis as penis abnormalities are rare, and almost all sizes are considered normal except for some severe exceptions.

A large-scale study published in the ANDROLOGIA in 2021 involving thousands of people noted that the average length of a fully erect penis is 16.78 cm (6.60 inches) with an average circumference of 12.03 cm (4.73 inches). However, the size of a flaccid penis was less, with an average length of 9.47 cm (3.72 inches) and a circumference of 9.59 cm (3.77 inches).

A significant variation exists in the size and shape of the penis.


However, each study gives different results depending on the nature of the study group involved and the sampling criteria. But, the average length in most studies is 5.1-5.5 inches for a fully erect penis.

As with other organs, many people will lie at the extremities and have an extremely large or small-sized penis. If your size is slightly more or less than this average, there is nothing to worry about, as it is known that penis size doesn't matter too much in sex. Despite all these societal myths, penis size and shape are not much related to race, ethnicity or hand and shoe size. No credible studies have backed these claims.

What should the top 'glans penis' be like?

The glans penis is typically comma-shaped or acorn-shaped. The word 'glans' actually means acorn in Latin. Although the anatomical description is defined, the exact shape and size of the glans penis have person-to-person variations. It can be narrower in some people but bulbous and large in others.

A larger glans penis increases the chances of leaving babies in a competitive environment.


The skin on the top has a smooth appearance and texture. However, it becomes scaly or wrinkly due to irritation and dryness. The shape of the glans penis can, however, sometimes also change due to some conditions like pearly penile papules (non-cancerous growths), which result in the formation of tiny bumps around or on the corona of the glans penis.

Why is your penis mushroom shaped?

Let's come back to the main topic. How has the shape of the human penis evolved and why is the penis mushroom shaped? Various theories have tried to explain it. Let's review some.

It's an evolutionary adaptation.

Evolutionists study the process of gradual change in living organisms. According to the evolutionist, no change in the human body has occurred overnight. It developed over a long period, and the selection pressure provides the primary stimulus for the difference.

Semen displacement hypothesis

It is a popular theory proposed by Professor Gordon Gallup and his colleagues in 2004. It was published in Psychology and Counselling.

According to this theory, the shape of the glans penis is an evolutionary adaptation that allows the penis to displace the sperms of other sexual rivals from the female vagina. If this seems bizarre to you, don't forget that the evolutionist's point of view is that humans have evolved from animal ancestors. Let's look at the rationale behind this theory.

The variations in the penis shape caused a selection pressure

The evolutionary changes develop over hundreds of thousands (even millions) of years and grow from the requirements of survival in a new environment. In the early times when humans were evolving from their ancestors, it was common for a woman to have many sexual partners.

The human penis evolved slowly with human evolution.


In those pastoral and nomadic societies, women were often encouraged to engage in sexual activities with multiple men to produce maximum babies. Because of this, her vagina is likely to have sperm from multiple males, so, to improve the chances for a man to father a baby and displace the semen from rivals with his own semen, the shape of the penis should be such as to scope out the sperm from other rival males.

People with a pronounced coronal ridge and glans win

In short, only the males having these penises were able to produce babies, and with time, this adaptation was fixed in the human population. The men with narrow heads (without more prominent glans) could not pass their genetics on to the next generation, therefore, their physical attributes, such as the shape of their glans, disappeared gradually.

A bigger glans penis produced more vigorous thrusts

Another argument was that a more prominent head facilitated a more vigorous thrust which enabled the replacement of semen. So a more vigorous thrust coupled with the mushroom-like shape secured a victory for these males over their competitors.

Is there any evidence?

This theory may seem logical, but is it backed by any credible research and what does the scientific community think about it? After all, there are a lot of ambiguities surrounding this aspect of evolution. Human sexual behaviour is more complex than animals and is influenced by many other factors.

The arguments by Professor Gordon Gallup and his colleagues

The theory might be bizarre, but some research backs it. Professor Gallup and his New York State University colleagues investigated the anatomy and evolutionary history of the human penis in 2003. They found two critical evolutionary changes.

  1. The glans penis

  2. The ridge that separates the glans penis from the shaft

They noted that both of these features help in the clearance of sperm from the competitor males from the vagina. Hence, a new partnership with a stringer ridge (well-developed glans) and more vigorous thrust can displace foreign semen and leave more offspring than the other males. Thus, these adaptations were transferred to the next generation.

Experimental verification

Some researchers tested this theory in the labs using an artificial vagina and latex penis. Using a mixture of water and starch as a semen substitute, they noted that the ridge and glans together could clear more than 90% of the semen substitute with just one thrust. They explained that this challenge resulted in the evolution of penises with more vigorous thrust and prominent glans.

The theory received mixed opinions from the subject experts.


The change also appeared in human psychology as the researchers noted that couples tend to engage in more energetic thrusts if they have been apart for a long time, particularly if the female partner is suspected of cheating. They explained that it stemmed from the subconscious desire to cleanse his partner of traces of semen from the competitor males.

Longer penis Vs. Bigger glans penis

Another researcher noted that having a longer penis was not so beneficial as the sperm could travel towards the required site by themselves. But, having a penis with wider glans provided an edge as it could open the vagina and scope out the sperms from previous males to maximize the chances of paternity.

This theory explained the evolution of the penis, although the cleansing action may not be as valuable to men these days.

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How has the scientific community received this theory?

The theory received mixed responses. It may seem strange to you. But how accurate is it? According to the experts, it is a logical one, but not 100% accurate. The reviews of some experts are;

Dr Sarah Melancon

Dr Sarah is a clinical sexologist and sociologist. She appraised the theory but also noted various significant loopholes in it. One important thing to consider is the mechanism of ejaculation and fertilization.

Inside the female body, the sperms can stay alive for up to 5 days, During this time, the cervical mucus protects them. If there is no mucus, the highly acidic environment in the vagina will kill the sperm instantly. With this factor in mind, the displacement of semen can be a problem if the woman has undergone sexual intercourse with various men within a few hours or during ovulation. Nevertheless, she called this theory a 'real one'.

Dr Daniel Boyer

Dr Daniel Boyer is a clinical pathologist and Associate Professor of Pathology at the University of Michigan and he disagreed with this approach and exclaimed that the mushroom shape of penises had evolved to create more pleasurable sensations for both partners. This shape is more of a physical adaptation to facilitate successful mating with improved efficiency.

According to him, this shape gave the penis a more appealing look to the female partner.

When should you be worried about the shape?

Whether you want to believe in this evolutionary theory is not as important as the health of your penis. Slight variations in the shape are typical. However, you need to consult the doctor in case of sudden and unexpected changes in the body, texture or appearance of the glans penis, particularly if you have the following signs too,

  • Painful urination or blood, mucus etc., in the urine

  • Abnormal discharge from the penis

  • Lesions, e.g., sores and bumps

  • Rashes and redness

  • Bleeding, swelling and pain on any part of the penis

The doctor will diagnose the condition and give proper treatment. However, some situations may require you to visit a dermatologist or urologist.

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The penis has a central role in sexual activities. The glans penis or penile head is the tip of the penis, giving it a mushroom shape. The exact appearance of the penis glans penis can vary, however, these variations are perfectly normal.

The glans penis is usually smooth in texture and has a lot of nerve endings, making it very sensitive. Besides its role in sexual intercourse, it also has the opening of the urethra and is involved in urination and the ejaculation of semen. It also facilitates easy penetration and forceful thrusts during sex.

The shape of the glans penis has attracted the human imagination, and various myths developed over time and multiple theories based on different arguments have developed. Two decades ago, the semen displacement hypothesis, proposed by Professor Gordon Gallup, provided an evolutionary insight into the development and evolution of the human penis.

This hypothesis has explained the evolution of the glans penis with a need to remove the semen of other males from a woman's vagina. A penis with a larger cap 'glans' at the end pulled the semen of other males more effectively than a straight penis would. It also provided more forceful thrusts, which further facilitated the job. However, various opinions also exist. The male has their own uniquely configured penises.

It is up to you whether you want to believe it. 

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