I am one of four children all with the 'same' upbringing but all completely different in looks and temperament.
Given that we all had the same evil mother and all went through the same experiences we have nothing in common and actually do not talk to each other and haven't in years - since my mother's funeral.
I believe nature has more to do with it than nurture.
My daughter looks exactly like me, everyone comments on it, however she has her dad's nature, annoy her and she can sulk for England. My son and me share the opposite personality, we put someone firmly in their place and forget about it. I always wonder how really bad characters sometimes come from lovely families when they are brought up well.
Look up epigenetics. The answer is both. The environment can switch on or off certain genes, so to create an individual both nature and nuture have just as much an effect on that person.
Both have an equal effect on a person. Read my previous comment. Feel free to argue with me, but my degree is biological anthropology and so I've spent years studying this 'trick' question.
It's not just a mixture of the two either- it's also how they combine together which is unique. The same experience or upbringing for one person, will affect them differently than someone else because their character interprets and deals with it differently.
Both sons (16 months between their ages), both brought up similarly, I can see bits of Mr Alba in both and bits of me too.
Each has turned into their own man though but both are caring and have a wicked sense of humour.
I think it's a bit of both. We have three, consciencely bringing them up the same and never ever played one up against another, as my parents were wont to do. They all have vastly different personalities, but their life values are the same. I believe as parents we are duty bound to teach them right from wrong, good manners etc. Hard work when they are small, it is much easier to say yes to everything, saying no is hard sometimes, but when they get older you can see the fruits of your labour.
My eldest daughter is the complete opposite of me, the younger one is so like me in many ways, both brought up the same. Younger daughter's children, girl, absolute image of her and so like her mum when she was a baby, looks and temperament, buy, 11 1/2 months younger, image and temperament just like his dad. So my answer is, I don't know, your guess is as good as mine.