I actually just read a fascinating article about recent research that showed that the instinct for revenge and the instinct for forgiveness were both innate, yet influenced by environment.
Basically, the theory is that, in situations in which strength is paramount for safety, the instinct for revenge takes the lead because you're less likely to be attacked if you make an example of someone.
Similarly, in situations in which cooperation is more conducive to survival, the instinct for forgiveness becomes more pronounced.
That makes sense. I guess I was thinking from my comfortable middle-class context, where it's more common to watch Bad Things on TV than to experience them personally. But certainly there are situations in which survival makes compassion a liability.
not an either/or
Basically, the theory is that, in situations in which strength is paramount for safety, the instinct for revenge takes the lead because you're less likely to be attacked if you make an example of someone.
Similarly, in situations in which cooperation is more conducive to survival, the instinct for forgiveness becomes more pronounced.
(If you're interested, you can download the article at http://greatergood.berkeley.edu/greatergood/2008spring/.)
Re: not an either/or