Human testicles vary in size, but new research finds the size and shape of your balls may explain more about you than you think. So, today we are going to explain the shocking science behind human testes. Unlike an elephant, where the testicles are deep within the body cavity, us primates have ours hanging outside of us in a sack. And compared to dolphins whose testicles are huge and make up around 4% of their body weight, the equivalent of human testicles weighing roughly 9.9 lbs or 3 kg, you might think in general ours are small. But to understand more about our human testicle size and how your junk stacks up, we shouldn't be looking at other species like dolphins, but at our fellow primates. Relative to body weight, the human testicle is triple the size of a gorilla, but 1/5 that of a chimpanzeee. The variation in testicle size amongst primates has to do with two scientific concepts. Pre-mating and post-mating sexual selection. Pre-mating sexual selection in primates involves badges of status. These are physical traits that signal social dominance and the potential for male reproductive success. Essentially, badges of status are physical appearances that help male primates get laid. Examples include the larger noses of the probosus monkeys. The larger the nose, the more likely to get laid. Other examples include the redder the patch of the galades or the larger the cheek flanges of orangutans. Some studies indicate that the thickness of beards in homo sapiens could be a pre-mating badge of status. This is my badge of status, y'all. Is it working? Ding. Delete that. Post-mating sexual selection has to do with the sexual selection that happens after the primates have gotten laid. For example, the quality and amount of sperm production happening within the testicles themselves. Male success relies on a combo of pre-mating success and post-mating success. What is fascinating is that research has found the showier the badge of status, the smaller the testicles, aka large flange, small balls. Large nose, small balls. The redder the patch, smaller the testies. Being able to grow a beard. This led researchers to do more studies, including one on howler monkeys. And again, it was found howler monkeys with the most developed thyroid and larynx, aka the ones who could broadcast the loudest low forant frequency vocalizations used to attract mates, had the smallest balls. And even study on human male testicles found correlations to voice pitch. Men with lower, more attractive sounding voices tended to have lower sperm counts. So what is happening here? It's most likely due to the evolutionary trade-offs between prenating and post-mating sexual selection, aka the energy needed to maintain these physical badges of status versus the energy needed to maintain testes mass. It's been found that the larger the testicles, the more sperm produced. And this has been well established in human males, too. Men with larger testicles generally produce more sperm. And that's likely due to the simple fact that larger testicles contain more seminifpherous tubules, which is the sperm producing tissue. In the animal kingdom, the males that invest increased energy into badges of status have more access to females, therefore decreasing their need to invest in testicular size because there's less sperm competition between males. The big nose gets them laid, so they don't need bigger balls to produce more sperm. So, increased investment by males into badges of status decreases sperm competition, which then relaxes the selection pressure of sperm production, ultimately decreasing ball size. Make sense? Extrapolating to humans here, maybe men who can grow the thicker beards do have the smaller crown jewels. There is no adequate studies on this, but one survey and study found men with larger testes spent less time doing child care, less time changing diapers, and less time looking after their family compared to men with smaller balls. Small balls equals better fathers. This does kind of link to other studies on primates. These fine gorillas and colobos monkeys have smaller balls because they are more likely to mate exclusively. Whereas apes who have sex with lots of partners like macaks have larger balls due to sperm competition. Maybe the men with big balls are bad dads because they're less likely to want to be monogamous and are therefore less caring towards their families. Is an extrapolation, but maybe if you are looking for a committed partner, but he's got big saggy droopy balls, it's time to run. Again, there are no valid studies on that. But what about the droop? What if one hangs lower than the other? Human scrotal descent is likely linked to the fact that sperm production and storage is maximized at cooler temperatures. It's why the skin on our scrotal sack is so thin and why the arteries that supply blood to the scrotum are right beside the veins. Another cooling and heating exchange mechanism to keep the balls cooler. In general, scrotal temperature is 2.5 to 3° C lower than body temperature, which is most efficient for the creation of sperm. It's also why when it's cold outside, the scrotum shrinks and pulls closer to the body to use its warmth and keep the testicles at the correct temperature. There are muscles called cremisteric muscles which serve to retract when it's cold and relax when it's warm to regulate that temperature. The interesting thing is that each testicle moves in its own orbit as a way of maximizing the available scrotal surface for cooling. So for this reason, there's a lot of lopsidedness in the balls as the testicles try to cool themselves independently. Also, the sack will tighten and the balls will move closer to the body upon arousal, likely to help the sperm warm up and prepare for ejaculation into the warm vagina. But it also has another added evolutionary advantage, keeping the sack and the balls closer to the body during the vigorous thrusting of sex as to not damage or hurt them. And as for the droopiness of the ball sack, this will vary from one man to another. Just like some people have different sized hands, some people have different sized spermatic cords or a scrotum with more surface area and looser volume. Okay, this can sometimes lead to a droopier default position. I don't know what else to tell you except that one thing is for certain. Everyone will age and the skin will lose elasticity and collagen throughout your body. So, yes, as you age, your balls will become drippier. That's an exciting thing to look forward to. Enjoy, y'all. And if you've ever noticed that one ball is larger than the other, that's completely normal, too. In fact, for most men, the right testicle is slightly larger than the left. Whereas the left testicle is more likely to hang lower. Again, this all links back to your personal anatomy. At the end of the day, if your balls hang low, if they wobble to and throw, if you can tie them in a knot, if you can tie them in a bow, if you can throw them over your shoulder, you likely have a Guinness World Record and should probably contact someone. But truly, as primates, our testicles shape and size and droopiness are a fascinating part of our evolutionary history. There's even some recent research on sexual selection, proving that our ball size compared to other parts of our body is likely to change more due to evolutionary pressures. Therefore, in the future, our balls might shrink or grow. And looking into the past, they've had many different sizes and shapes leading up to our pre- ancestors. Thank you so much for watching this video. Honestly, we found this information fascinating. Your balls are very intricately linked to evolutionary history in primates, which you are. You're an animal, bud. Thank you so much for watching and we will see you soon for a new science video. Awesome. Peace.