Agression: Men vs Women

I'd prefer an answer to this from someone who is actually a psychologist
(not a psychologist wannabe). If none are here then info from anyone else
will be appreciated

Take a large random sample of men and a large random sample of women (From
American society if that matters). Is there any research which has
compared
the average levels of aggressive behaviour between these two samples?

Or the short version of this question - Is there evidence that men are
more
aggressive then women.

Aggression in the sense of violence.

If there is a difference is there a breakdown as to why? Is it
inate/biological or is it cultural?

Thanks

Pete