I think it is a combination. LOL. I know for a fact that my sons were both born with individual quirks to their personalities. My first is intense, worrier, brooding and can be quick to anger. My second is laid back, happy go lucky, almost always in a good mood and rarely gets upset. They were born 15 months apart so the parenting and environment is the same. But then you see as they get older, your child will say something that you are like "OMG, that's ME" and that can be scary as they may mimic our worst qualities. ugh.
And certainly, a child born into a home with great dysfunction, that is going to cause a person to react to that environment and it WILL have an affect.
But I definitely think we are born certain ways. And then that is added to by our home life (and friend life and school life and work life . . . as life goes on).
It depends. For some behaviors it's mainly 'nature'. For others it's 'nurture' but for most it's both. Parental influence can bring out, amplify and encourage the development of those innate potentials, talents, biases and behaviors that are good and suppress others not so good. It shapes you, creates the you that you are. Generally speaking, that is. Just guessing. I don't know for sure, never had the pleasure of being a parent. What an awesome job that is. God bless all of you who are.
Not done talking about this yet. ;D
I think basically mammals are very similar to each other, and that's why behavior studies on rats and dogs work and are applicable to humans.
So look at the dog breeds. By careful selection, you can breed a dog that will either guard or will not, will be gentle and loving or who will not, will hunt to exhaustion or will not, will be obsessed with chasing vermin down and killing them or will not, will be able to herd other animals or will not, etc. You can breed those dogs, and expect that most in the litter will have the skills of the parents.
Certain dogs are meant to work alone, and certain dogs are meant to work in small groups and are bred for those abilities and the ones meant to work in groups will not attack other dogs.
When I look at how you can selectively breed for personality and ability in dogs, I have to think personality and abilities are genetic.
You just don't see it as clearly in humans because no one has spent 1000 years trying to selectively breed for traits. We mate for love.
Wow life! Funny, I think we're almost 100% nature.
I am so surprised at the things I've seen in my kids, that appear to be genetic and not learned.
For example, this thing we call the "flashlight gene". An apparent liking or disliking of something that seems genetic, named "flashlight gene" by a friend who had 2 generations in her family of toddlers who were obsessed by flashlights.
We saw it in my family with turtles, and sewing machine bobbin cases - things that are kind of unusual to have obsessions over, and weren't introduced to the kids - they found them and became intrigued to the point of near obsessions.
I've seen some kids who are born rule-followers and are organized, and some who are born disorganized and pushing the rules. From birth.
Twin studies of twins separated at birth can turn out amazingly the same. Astoundingly the same, really, considering how differently they were raised.
The greatest determiner of criminality in the son is criminality in the father, even if the son never knew his father and didn't know his father was a criminal. How wild is that?