In Man of Steel, the villain is General Zod--a born and bred warrior who is singularly purposed with protecting the people of Krypton (home planet of Superman). It appears that the Kryptonians have engaged in some poor planet managing over the years and have
Thirty-three years pass and Zod is drawn to Earth where Superman has landed. It is on Earth that Zod lays out his plans for the future of Krypton--He plans to transform Earth's atmosphere so that it will be hospitable to Kryptonians (and fatal to Earthlings, but YOLO).
In Superman's subsequent interactions with other members of Zod's goon squad, he learns why Zod is unwilling to share the planet: It is because of a rather inflexible belief in Social Darwinism--the thesis that some groups of individuals (Kryptonians) are inherently better than others (Earthlings).*
*It is a rather egregious plot hole for a member of Zod's company to specifically discuss Evolution as a reason why all Earthlings should die in favor of Kryptonians, given that Evolution is a theory from 19th century Earth.
Social Darwinism is not unique to crazy Generals from outer space. It's actually a social ethos that has been a large part of human society for centuries. It was in the 19th century, for example when so called scientists used fraudulent scientific methods to suggest that certain races were inherently superior in head size (and thus, intelligence) than other races. Before that time, European royalty often relied on blood lineage to determine the fitness of individuals to rule. Even in contemporary American society, high status individuals in society are often more likely to favor what are called essentialist beliefs about social categories--that is, beliefs that social categories are stable, inherent to individuals, and biologically determined. These beliefs allow high status individuals to rationalize their elevated positions in society, and to explain why they have so much, while others have so little (e.g., because my genes are better than yours).
Last month in the Journal of Personality and Social Psychology, my mentor Dacher Keltner and I published a paper examining essentialist beliefs related to social class categories. We reasoned that upper-class individuals--those at the top of society's hierarchy--would be more likely to believe that their elevated position in society was based on internal, stable, and genetic factors then would their relatively lower-class counterparts. That is, high status individuals would reason that their elevated social position was due, in part, to better genes and biology.
This is precisely what we found. Across studies, people with higher income, and who ranked themselves high in social class--on a ladder with rungs representing society's hierarchy--tended to reported elevated essentialist beliefs about social class relative to their lower-class counterparts. For these individuals, being high in status is justified by one's superior genetic predispositions.
Social Darwinism, and even essentialist beliefs, have consequences for how people treat each other. In the Man of Steel, Zod and his people justify their destruction of Earth by reasoning that Kryptonians are inherently more valuable than Earthlings. In our own research, people who endorsed essentialist beliefs about social class categories were less likely to favor restorative justice--justice proceedings that focus on helping individuals to avoid future law-breaking behavior through rehabilitation. Essentialist beliefs necessarily suggest that rehabilitation will be ineffective in changing people with bad genes.
So there you have it, some very real psychological processes driving the plot in one of the summer's most explosion-heavy blockbusters! SCIENCE + EXPLOSIONS!
Kraus MW, & Keltner D (2013). Social Class Rank, Essentialism, and Punitive Judgment. Journal of personality and social psychology PMID: 23713698