Why did humans evolve big penises but small testicles?

We have the penis of a monogamous primate yet our body sizes suggest our ancestors slept around a lot.

What led to the evolution of African men with big penises, while

The Erotic Endurance of Whale Hips

How come you never see any gorillas who are hung like a horse below the belt? - Quora

Penis evolution across species: divergence and diversity

Male walruses have giant ones, but human men not at all: How we

The Reason Why Men Have Nipples

Why did humans evolve big penises but small testicles?

Bipedalism and Other Tales of Evolutionary Oddities

Ancient humans lost their penis bone for a…

Science - Gayety