The BBC reports that oxytocin, a natural brain hormone, has been used via nasal spray to create trusting behavior during simulated negotiations between "investors" and "trustees" during a Swiss study. It dramatically increases investor trust but doesn't affect trustee behavior. Another researcher points out that while many may fear politicians may spray their rallies with the substance, the reality is release of the hormone by well crafted stimuli may be behind much of the current techniques used by marketing firms. Interestingly it doesn't seem to affect investors when the trustee is a computer.
They claim autism may be treated with this drug. I am highly skeptical. While this drug affects the amygdala, which is also implicated in autism, the asocial behavior of autism seems less to do with critical thinking getting in the way of social trust than to do with destruction of the amygdala's function. The amygdala is the organ that shrinks the most upon castration of adult males, and its development during adolescence is debilitated in autists. Autists seem to lack a sense of territoriality -- and they rarely if ever sire children (most are male). Oxytocin may create more problems than it solves for autists.
What I find intriguing is the possibility that groups that have lived in diaspora among others may have evolved mechanisms for manipulating oxytocin secretions to which they are relatively immune. It would make perfect sense to do so. They may have even evolved pheromonal secretions that stimulate, simulate or actually are oxytocin aerosals such as those studied by the Swiss researchers. How do various ethnic groups rate on scales of "trust" of others?