Who’s Got the Biggest BALLS of Them All??

It wasn’t but a few weeks ago that I was faced with something far outside my comfort zone. Metaphorically speaking, my toes were hanging over the edge of the cliff and my heart was pounding. It was then that I asked myself… “Do I have the balls?”

Now, before I could take ‘the leap’ I was immediately distracted by my minds use of the comical saying. Where did it come from and why do big balls equate to something exceptional?

Before long I found my answer…. sperm competition and female promiscuity.

When you think about it, it’s obvious that our current sexual anatomy and physiology give us hints about the sexual behaviour of men and women during human evolution. For example, there is a direct relationship between testis size in a species and the degree of female promiscuity. When females are promiscuous, the competition between males of some species can continue AFTER mating – by means of sperm competition. The insertion of the penis can cause the ejection of sperm already present in the female from a previous mate, or part of the males ejaculate may coagulate into a dense plug that prevents later insemination by other males.

In species in which sperm competition is high, penises tend to be longer and testes larger so that a large number of sperm can be produced. For example, sperm competition is much more intense among chimpanzees than among gorillas, therefore the size of the testes is much greater in chimpanzees. In pigs (where mating is extremely ‘loose’) males have penises long enough to deposit semen directly into the females uterus and ejaculate can measure a pint or more in volume!

So how does the size of human testis compare?

The human testis, at 10-14 grams each, lie about halfway between those of a chimp and a gorilla (after accounting for differences in overall body size). Turns out, humans are about average-sized among primates as a whole. So what does this suggest? Female promiscuity and sperm competition have been factors in human evolution…..

And, the male with the biggest balls really does get the women.