The exploration of politics in science fiction is arguably older than the identification of the genre. One of the earliest works of modern science fiction, H. G. Wells’ The Time Machine, is an extrapolation of the class structure of the United Kingdom of his time, an extreme form of social Darwinism; during tens of thousands of years, human beings have evolved into two different species based on their social class. Speculative societies Most story and novel-length works of science fiction include speculation (directly or indirectly) on modes of life and behaviour. They are sometimes allegorical and often serious attempts to model possible future societies, political institutions and systems. Examples include Harry Harrison's novel Make Room! Make Room!, The Dispossessed by Ursula K. Le Guin; and the Hostile Takeover Trilogy by S. Andrew Swann. Imagined societies may be based on very different assumptions. Often the future is modeled on historic forms - feudalism, or in the case of The Foundation series, the Roman Empire. A common theme is the integration of humanity into some greater interstellar society. A popular modern example is the Uplift series by David Brin where a species' status is defined based on the concept of biologically uplifting other species. Utopian societies The term utopia was invented by Thomas More as the title of his Latin book De Optimo Reipublicae Statu deque Nova Insula Utopia (circa 1516), known more commonly as Utopia. He created the word "utopia" to suggest two Greek neologisms simultaneously: outopia (no place) and eutopia (good place). More depicts a rationally organised society, through the narration of an explorer who discovers it—Raphael Hythlodaeus. Utopia is a republic where all property is held in common. In addition, it has few laws, no lawyers and rarely sends its citizens to war, but hires mercenaries from among its war-prone neighbours. Generally speaking, utopias are generally societies whose author believes either perfect, or as perfect as can be attainable. Ernest Callenbach's Ecotopia is a contemporary example. This can cause some confusion, in that some works generally recognized as “utopian”, such as Plato's Republic, can come across as much less than ideal to a modern reader. They are one of the smaller subsets of political science fiction, possibly because it is difficult to create dramatic tension in a world the author believes is perfect. Various authors get around this problem by postulating problems in the utopian society, such L. Neil