Researchers have long examined whether the size of a man’s testicles is associated with specific biological traits or behavioral tendencies.
Although the subject may seem unusual, multiple scientific studies have explored potential links between testicular volume and reproductive capacity, hormone levels, and even aspects of behavior. A widely followed educational YouTube channel has also addressed the topic, suggesting that factors such as sperm production and vocal attractiveness may correlate with testicular size.
The channel, AsapSCIENCE, founded by Mitchell Moffit and Gregory Brown after they met studying biology at university, is known for translating academic research into accessible animated videos. In one episode, the creators reviewed several peer-reviewed studies focused on reproductive biology and evolutionary theory to explain what science currently suggests about testicle size.
What is considered average?
According to Healthline, the typical dimensions of adult male testicles measure approximately 4 x 3 x 2 centimeters. Minor asymmetry is common and not considered abnormal. In many cases, the right testicle is slightly larger, while the left tends to hang lower.
Bupa notes that healthy testicles generally feel smooth and firm, though not rigid.
Evolutionary theories and sperm production
In their analysis, the AsapSCIENCE hosts discuss differences in scrotal size between humans and other primates. They connect these variations to evolutionary concepts described as “pre-mating” and “post-mating” strategies.
In certain monkey species, reproductive success before mating depends on visible dominance signals. After mating, however, success relates more closely to sperm production—both quantity and quality.
Studies on howler monkeys, for example, observed that individuals producing the deepest, loudest calls tended to have smaller testicles.
When examining humans, the creators cite research suggesting that men with deeper, more attractive voices may also have lower sperm counts.
Broadly speaking, larger testes are typically associated with higher sperm output. Separate research has also explored whether testicular size might correlate with paternal behavior. Some findings suggested that men with larger testicles devoted less time to childcare and family engagement, while those with smaller testicles demonstrated more nurturing tendencies. However, researchers emphasize that this relationship is not definitively established and remains theoretical.
This topic has received less public attention than the informal idea known as “summer long balls,” a reference to how warmer temperatures can cause the scrotum to hang lower as part of natural temperature regulation.
Health implications
Medical News Today reports that testicle size alone does not determine a man’s overall health status. Nonetheless, testicular volume is connected to sperm count.
A study published in 2022 found that children and adolescents who were overweight or insulin resistant were more likely to have smaller testicles, suggesting a possible association between metabolic health and testicular development.
Rossella Cannarella, M.D., of the University of Catania, said via the Endocrine Society: “More careful control of body weight in childhood and adolescence may help to maintain testicular function later in life.”
Testicular shrinkage may also occur due to testicular atrophy, a condition that can affect one or both testes. Symptoms may include reduced libido and infertility, with causes ranging from aging and inflammation to steroid or estrogen use.
In addition, testicular cancer can alter the size, shape, or texture of a testicle. Cancer Research UK advises that swelling, the presence of a lump, or one testicle becoming noticeably larger than the other may be warning signs.
Medical professionals recommend consulting a GP if any unusual changes are detected, as early evaluation is essential for accurate diagnosis and treatment.
