Is aggressive behavior environmentally or biologically based?

Any behavior, including aggressive, would most probably be both environmentally AND biologically based. This goes back to the old argument, which is more important to an individual--and has the most effect--inheritance or environment.

The answer is always the same. The genetic inheritance an individual receives determines the intelligence, basic skills, personality and ability he can use

throughout his life, and is basically a gift from his ancestors. Environment, on

the other hand, are the surroundings the individual either seeks or falls into

by happenstance. Altough his genetic inheritance would determine his penchant

and propensity for aggressiveness, his environment would determine whether he

actually acted on his aggressive tendencies.