Humans have a natural propensity towards violence"
No they haven't - if that was true, there are a hell of a lot of humans, so we really should go out in body armour every night.
I think I've only ever personally encountered violence once in my life (having lived in rough areas in three of our major cities)- when I was beaten up by three Chelsea supporters (not sure supporting Chelsea qualifies them as being human)
The overwhelming mass of humanity is peaceful by inclination - television and violent video games are impinging on humaities acceptence of violence, but hopefully, like pop music, they'll grow out of that.
I genuinely believe this has always been the case, even moreso nowadays,

Favourite poem.

The Man He Killed
Thomas Hardy

"Had he and I but met
By some old ancient inn,
We should have sat us down to wet
Right many a nipperkin!

"But ranged as infantry,
And staring face to face,
I shot at him as he at me,
And killed him in his place.

"I shot him dead because —
Because he was my foe,
Just so: my foe of course he was;
That's clear enough; although

"He thought he'd 'list, perhaps,
Off-hand like — just as I —
Was out of work — had sold his traps —
No other reason why.

"Yes; quaint and curious war is!
You shoot a fellow down
You'd treat if met where any bar is,
Or help to half-a-crown."

Jim Carroll