“Size matters” is often dismissed as a tabloid cliché, yet for evolutionary biologists, the dimensions of the human penis represent a genuine scientific mystery. When compared to other great apes, such as chimpanzees and gorillas, the human penis is significantly longer and thicker than expected for a primate of our size.
If the primary role of the organ were simply to transfer sperm, humans would likely possess smaller anatomy similar to our closest relatives. However, a landmark study published in PLOS Biology suggests that the human penis evolved to serve two additional, critical functions: attracting mates and threatening rivals.
The Evolutionary Puzzle: Why So Prominent?
Understanding why the human body looks the way it does is a cornerstone of evolutionary biology. Scientists have long established that features such as greater height and a V-shaped torso increase a man’s sexual attractiveness. However, the evolutionary drivers behind penis size remained under-researched until recently.
The study points out that humans began walking upright long before the invention of clothing. Consequently, the penis became highly conspicuous to both potential mates and rivals during most of our evolutionary history. This visibility likely led to “sexual selection,” where certain traits are favoured because they provide a reproductive advantage.
The “Dual Function” Theory: Attract and Threaten
In the animal kingdom, many male traits serve a dual function. For example, a lion’s mane or a deer’s antlers are used to both attract females and signal fighting ability to other males. Researchers sought to determine if human anatomy follows this same evolutionary pattern.
Methodology of the Study
To test this theory, researchers presented more than 800 participants with 343 videos of anatomically correct, 3D computer-generated male figures. These figures varied across three specific metrics such as Height, Shoulder-to-hip ratio (body shape) and Penis size.
Participants viewed these figures either as life-sized projections or on personal devices. The team asked women to rate the figures based on sexual attractiveness, while men were asked to assess them as potential rivals, focusing on how physically threatening or sexually competitive they appeared.
Key Findings: Perception Among Men and Women
The results confirmed that size plays a significant role in social and sexual signalling.
• Attraction: The study reaffirmed earlier findings that women generally find a larger penis more attractive, particularly when combined with greater height and broader shoulders.
• Competition: For the first time, researchers determined that men also pay close attention to the size of their rivals. Men rated figures with a larger penis as being more sexually competitive and perceived them as more dangerous opponents in a physical confrontation.
Furthermore, these findings suggest that the human penis acts as a signal of “fighting ability” to other males, much like the ornaments seen in other species. By being highly visible, the organ provided a shortcut for ancestors to gauge the threat level of a rival without necessarily engaging in combat.
Q&A: Deep Dive into Evolutionary Biology
Q: How does the human penis compare to a gorilla’s? A: Despite their massive body size, gorillas have very small penises, usually measuring only about 3 cm when erect. Humans are unique among primates for having much larger organs relative to their body size.
Q: Does height matter more than size? A: The study found that women prefer a combination of traits. While a larger penis was rated as more attractive, height and a broad shoulder-to-hip ratio were also essential factors in overall attractiveness.
Q: Did the invention of clothing stop this evolution? A: The study does not explicitly date the end of this evolutionary pressure. It notes that the penis was conspicuous for “most of our evolution” before clothing was adopted. This was the period when these traits were likely selected.
FAQ: Frequently Asked Questions
What was the main discovery of the PLOS Biology study? The study discovered that human penis size likely evolved for two distinct purposes. One purpose is to attract female mates. The other is to intimidate or threaten male rivals.
Why do researchers compare humans to other great apes? By comparing humans to chimpanzees and gorillas, scientists can identify “puzzles”—traits that are unusual for our species. The human penis is an outlier because it is much larger than those of our closest relatives.
How many people participated in this research? More than 800 participants took part in the study, viewing hundreds of different 3D male models to provide their assessments.
What is a “dual function” trait? A dual-function trait is a physical feature. It serves two evolutionary roles at once. It attracts the opposite sex (inter-sexual selection) and intimidates the same sex (intra-sexual selection).
Was the study done with real people? No, the study used 343 anatomically correct, 3D computer-generated male figures. This approach ensured that variables like height and body shape could be scientifically controlled and measured.
