Nature or Nurture Debate

Are there other theories besides nature and nurture that might explain the variability of human behavior? Please explain in as much detail as possible. Thanks for any help anyone can give :-)

Tibetan Buddhism (as I understand it... but check with someone smarter :-) ) argues that we behave the way we do because of our deeply engrained habits and karmic dispositions. Basically, the more we practice a behavior, the more automatic it becomes. We carry this from from life to life... but there is always a possibility to change and eliminate negative behaviors and adopt positive behaviors, although it takes a very long time and much hard work.

Some of the debate can be resolved by studying identical twins. Since they have identical DNA, most of their common behaviors would fall on the nature side of the debate and their differences on the nurture side. Behaviors on the nurture side can be from many different sources as skyDancer suggests and surely habit is a big one, especially what subjects you habitually think about.