Here's an interesting evolutionary concept of the penis.
Chimpanzees have relatively large penises and testicles, relative to their body sizes. They are not monogamous.
Gorillas have relatively very small penises and testicles, relative to their body size. They are monogamous.
Human beings fall in the scale of having larger penises and testicles relative to their body sizes (for example, if our penises were comparable to a gorilla's, relative to our body sizes, our dicks would be on average 2/3 of inch long...I feel confident in saying that most of us do not have this problem).
Using this logic, it would seem that human males are not designed for monogamy.
