What's with men and infidelity?

An old colleague of mine once said to me:
"Women are the soil. They are made to be planted.
While Men are seeds. And they are made to spread their seeds all over the place."

Of course, I quickly glared back at him.

But what is it with men and being unfaithful?
Is it true that 2 out of 3 men cheated on their partners?
Is it why that Islam - during very strict requirements - allow men to have more than 1 wife?

It's no suprise woman have a hard time trusting men.
After all, in this world men are actually outnumbered.
We have more women living on this planet than men,
so it's no wonder there are a lot of cat fight going on in the mating game of humans.

But then again going back to the question...
what is it with men and infidelity?
Why does men seem to always have the urge to try "new territories"?
For you girls out there, how do you spot an asshole jerk like that?

Sometimes when I hear stories of men cheating,
I feel so blessed to have my boyfriend.
He's so truthfull and faithfull and soo patient (with me) - well so far...;P