Evidence for this is found when we look at how our behavior and moral code of conduct has changed through history. If we assume our natural inclinations haven't changed over the last few thousand years then this supports the idea that our behavior is powerfully influenced by social rules.
Our "morals" are very different to the average person a few hundred years ago. Take a look at some of the dysfunctional countries still struggling with human rights.
Friends of friends were traveling through China a few years back. The bus ride wound its way through a narrow mountain road. They came across another bus which had rolled of the road seriously injuring many people. Fortunately these friends of friends were mostly medical doctors. However the bus driver and the rest of the passengers didn't want to stop and help. The doctors had to plead and beg to get the driver to stop. No doubt they saved lives that day but imagine not wanting to stop and help your fellow countrymen?
You think Chinese have different "natural inclinations". I don't think so.
In the west we went through the same social stages as we see many countries going through now. Back in the old days the poorest paid the most tax (wealthy paid none). You even look like your going to step out of line and your killed in inventive ways. I'm very skeptical that the west has a more "moral" history than the east. We are just ahead by a few hundred years (no doubt the east will change rapidly in an age such as this). And we are still far from perfect!
A child is not born with clear morals, it doesn't realise that hurting other humans is unproductive and unnecessary. Society teaches us through operant conditioning what is most beneficial to the human race as a whole- we are kind to other people and rewarded, if we are cruel we are punished. This makes sense in terms of natural selection too, the more we help each other people prosper, the more chance that particular human we contribute something to our species that will help us survive. The idea that an architect made us moral because we're 'special' is ridiculous. No animal kills another just for fun, they do it to survive.
Indisputably, the two main natural inclinations that all humans share are to survive and to reproduce. As a result of these inescapable inclinations, one must adapt his/her morality to adequate such conditions. Our natural morality encompasses the means of approaching an end (i.E. Survival and reproduction). While one might argue that society solely influences our morality, we still have individual morals, aside from those presented by society, that may be in opposition to that of society's. When it comes down to it, our morals as individuals hold more weight/influence than that of societies.