But Santa is a very different sort of novel from those two American classics. Santa is a naturalist novel that one might also compare to Upton Sinclair's The Jungle or Theodore Dreiser's Sister Carrie. Literary naturalism supposedly made novelists into literary scientists studying human behavior much as naturalists might study a colony of birds, that is, through systematic observation. Literary naturalists more or less went out with notebooks to observe the social environments in which they planned to place their fictional characters. Federico Gamboa kept a detailed journal that reveals his observational notes for various scenes in Santa. He never recorded details of a Mexico City brothel, but this does not mean that Gamboa did no participant observation in that department, because he most certainly did. Here is the point: literary naturalists created quasi-documentary historical sources from detailed re-creations of social environments in crafting the settings for the stories they wanted to tell.

A surprising lot of naturalist novelists wanted to tell stories about prostitutes. Émile Zola, the leading exponent—and more or less the inventor—of naturalism wrote about a girl named Nana in his widely influential 1880 novel that takes her name. Gamboa even visited Zola in France, where he became linked, for a time, to a prostitute of the Moulin Rouge, whom he used as something of a nonliterary model for Santa. Likewise, a brothel piano player that Gamboa knew in Mexico City became the model for Santa's blind admirer, Hipólito. In their desire for an unsentimental, scientific understanding of human behavior, naturalists wanted to strip away the clothing of civilization to expose the human animal. That led them to portray socially marginal characters, whose animal instincts were thought to have been laid bare by corrosive poverty, pathology, and exploitation. Naturalists were particularly interested in showing how social environments determined their characters' behavior, how a nice girl like Santa, in other words, could end up as she did. Naturalists wanted to demonstrate in their characters and plots that sex—supposedly among the most animal of instincts—was a mainspring of human behavior.

The naturalist aesthetic, out of style for several lifetimes, is not itself a reason to read Santa now, of course. For most readers, the appeal of Santa will come from the fact that naturalist novelists really did know the everyday sorts of places and people portrayed in intricate detail in their novels. Following his French influences, Gamboa believed that a novelist's mission was to tell the composite stories of people whose lives were never recorded individually as biographies, to become, in words that he himself used, a historian for people without a history. This makes Santa an interesting lens through which to view life in Mexico City circa 1900.

Readers need a sense of the author and his historical moment in order to interpret Santa. Gamboa was born into Mexico's upper class in 1864. In his youth, he wrote the society column for a Mexico City newspaper. He then spent much of his life as a career diplomat in a variety of foreign capitals, eventually returning to Mexico to become a literature professor and a government minister. He lived in the United States several times in his life, including a year in New York, a stint at the Washington embassy, and a brief political exile in Galveston. He knew English well, but he was distinctly not an admirer of the United States. In keeping with a proud conservative tradition in Mexico, he warned against U.S. influence.