Is testicles size important?
It’s not a joke, the testicles were measured judiciously and impartially by scientists. If you want to know: in species with polygamous females, males have oversized testicles. Why? Because, in order to win the competition with the sperm of the rivals, they need many “players” (sperm). That takes someone to make them. That’s why the testicles grew.
Chimpanzees, for example, where females are polygamous, have testicles twice as large as gorillas, a species of monkey whose females are monogamous (serial monogamy, more precisely, centered on the alpha male). Arriving at the estrus, a female chimpanzee has, in one day, several dozen sexual relations with different males. Before being fertilized, it can reach the remarcable number of 3,000 copulations.
The “right whale” or “black whale” (polygamous females) has much, much larger testicles than the “gray whale” (monogamous females). Find out that those testicles weigh 500 kilograms!
If this theory is correct (the size of the testicles has evolved in correspondence with the sexual availability of females) the question arises whether in humans, the most interesting species of animals, the size of the testicles reflects a tendency towards polygamy or monogamy. With the mention that monogamy can be serial… Hint: The relative size of human testicles is intermediate between monogamous and polygamous species.
Just FYI, in bonobo monkeys, polygamy is in full swing: they have sex almost anytime, not just to reproduce, but to signal friendship, to share food, to play (recreational sex) and even to make the passage of time more pleasant.
Bonobo sex and society, By: de Waal, Frans B.M., Scientific American, 00368733, Mar95, Vol. 272, Issue 3