The realism and naturalism movements are extremely similar in that both depict everyday characters in real-life situations in which conflicts are psychologically driven. Both realism and naturalism also make use of realistic costumes and indoor stage settings that are believable. Yet, one way in which they differ is that naturalism is based on Darwinian ideas of evolution from a shared ancestry and of survival of the fittest ("Naturalism," Northern Virginia Community College).

In accordance with Darwinism, naturalistic works focus on themes that show human beings are controlled by their environment and genetics. Plus, since human beings are controlled by their environment, people can take no responsibility for their actions because the environment is a force that is beyond control. To capture the Darwinian theory of survival of the fittest, naturalistic works also develop themes concerning the individual's need to fight against the grain of society in order to progress ("Naturalism"). To capture human beings as prisoners of their environment, fighting against the grain of society in order to progress, naturalistic works depict characters in states of deprivation such as poverty, prostitution, or emotional agonies leading to suicide.

August Strindberg's play Miss Julie can be classified as a naturalistic play because it captures these Darwinian beliefs through the characters of Julie, daughter of a count, and Jean, valet to Julie's father.

Jean was born a commoner but longs to be an aristocrat, as depicted in the recurring dream he relays to Julie of climbing a tree to reach the nest of golden eggs atop. To achieve his desire, he is willing to leave his fiancée Kristin to run off with Julie, open up his own hotel, and purchase a title as a count. Yet, when Julie suggests they commit suicide, Jean changes his mind, tells Julie to run off on her own, and returns to his born destiny of servitude. Jean's inability to climb out of his state of servitude shows he is completely controlled by his environment and genetics, a theme found throughout naturalistic literature.

Just like Jean, Julie is actually descended of commoners. The only reason she is considered an aristocrat is because her family's title was earned through sexual favors performed by one of her ancestors. As Jean explains it, "The founder of [Julie's] family... was a miller whose wife found favor with the king during the Danish War." In other words, as recompense for seducing the miller's wife, the king granted the miller the title of count. The fact that Julie actually comes from common, humble beginnings helps explain why, during the course of the play, she prefers to socialize with the servants. When socializing with the servants, Julie is forced by her environment to return to her humble roots. Plus, through seducing Jean and behaving, as Jean puts it, like a "whore," Julie symbolically returns to her natural class status of commoner. Julie's symbolic fall from the status of aristocrat to the status of commoner shows she, too, is nothing more than a product of her environment and her genes. Plus, characteristic of many naturalistic works, Julie ends by committing suicide to escape the fact that she has fallen in status by giving herself to a servant.

Naturalism is an artistic movement that emerged from in late 19th century Europe and generates realistic theatre through three principles: 

1) The play must be a realistic study of human psychology and behavior, with "flesh and blood" characteristics. Miss Julie follows the realistic characters of Julie, a woman who is attracted to her social inferior, Jean, a manservant to Julie's father. A naturalistic play must also have a decidedly non-theatrical and non-flamboyant presentation; Miss Julie is set exclusively in the kitchen of the manor belonging to Miss Julie's father.

2) The play's conflicts must be significant and life-altering. The love affair between Miss Julie and Jean serves as this risky conflict which ultimately ends in tragic consequences for Julie when she leaves to commit suicide.

3) The play must be simple and not complicate the primary plot with unnecessary sub-plots. Again, this is emphasized through the play's singular focus on Miss Julie and Jean's unlikely socioeconomic-crossing relationship.

Naturalism, a late nineteenth- early 20th-century phenomenon on stage (and elsewhere), featured the dramatic enactment of everyday conflicts among everyday characters like Miss Julie (1888), as opposed to heroic or larger-than-life figures from the Classical and Romantic periods.  Ibsen, Strindberg, Chekhov, and others saw the modernization of the stage as a vital part of the artistic movement called Modernism (see Irving Howe), and peopled the stage with such figures as Hedda Gabler, Dr. Stockmann, and Uncle Vanya.  Miss Julie finds herself in a romantic conflict involving a servant, Jean, in what some critics see as a Darwinian "survival" contest between social classes. Émile Zola outlined the three important elements of naturalism: faire vrai, faire grand and faire simple--realistic, based on human psychology, and dealing with flesh-and-blood figures, not abstractions or idealized figures.