Perhaps the earliest known mention of true aliens doesn't really come from sci-fi works, but it very well could have been a catalyst. The French Astronomist Nicolas Camille Flammarion wrote a manuscript in 1858 called 'Cosmologie Universelle.'
In this work, he explores the theory of Mars' canals, suggesting they were built by advanced civilizations. He later wrote 'Real and Imaginary Worlds' in 1864 and 'Lumen' in 1887, where he expands on the idea of a range of exotic species, including sentient plants which combine the processes of digestion and respiration.
The fusion of science, science fiction and the spiritual influenced other readers. Imagine the authors who were exploring for ideas in the new literature genre sci-fi, what fantastical tales they could drum up with this plot device. George Griffith and Edgar Rice Burroughs are noted for being inspired by Flammarion's theories.
Another possible candidate who could be credited for the birth of the sci-fi alien is the Italian Astronomist Giovanni Schiaparelli, known for his research on Mar's "canali" or canals in 1877.
From the incorrect translation into the term "canals", various assumptions were made about life on Mars; as these assumptions were popularized, the "canals" of Mars became famous, giving rise to waves of hypotheses, speculation, and folklore about the possibility of intelligent life on Mars, the Martians.
While H.G. Wells War of the Worlds 1898 is the most famous of the earliest sci-fi literature mentioning aliens, 'The Germ Growers,' joint written by Robert Easterley and John Wilbraham, was published six years before Well's novel.
Their novel centered on the Australian Kimberleys where human characters bore witness to the activities of alien flying craft and even the concept of benevolent alien creatures. Clemson.edu describes the nature of aliens in this very early period of sci-fi as:
"Aliens are seen as Darwinian Competitors; The idea of invasion is supreme.; The view of the relationship between aliens and humans is similar to cowboys and Indians.; Aliens are not realistic; they are seen mostly as grotesque; and Specistic- The benevolent aliens are mamalian or avian while the malevolent aliens are reptilian or insectoid."
This article could be soley dedicated in exploring many other examples of aliens in early sci-fi literature, but this is a sci-fi movie site. Let's settle with the examples above for the literary arena and move on to the arrival of movie aliens. The sci-fi movie alien has some of the most visually iconic entities such as H.R. Giger's Alien creature, Steven Spielberg's E.T., among others.
The First Movie Alien
Anyone can easily find the first movie alien by simply googling those words, which the most common answer is Georges Méliès A Trip to the Moon 1902, featuring moon creatures called Selenites, which are nothing more than actors in simple costumes.
From this beginning, movie aliens were a rarity for the next four decades, with Flash Gordon's aliens, including the Martian villain Ming the Merciless, being the more high profile other-worldly characters.
It was the Atomic Age, the fifties, where the movie alien burst on to the big screen in greater numbers. From peaceful aliens with a stern warning for mankind (The Day the Earth Stood Still) to vicious aliens bent on replacing mankind (The Invasion of the Body Snatchers), the fifties offered up a wide variety of aliens in all their cheesiest glory.
Many of the alien creatures were quite ridiculous visually by today's film standards. Though there were exceptions such as Forbidden Planet which used animation to create ferocious alien creatures. Many of the fifties aliens were similar to humanoid shape, but there were exceptions to that also such as Steve McQueen's The Blob 1958.
In the sixties, the movie alien more or less disappeared once again with very few films featuring E.T.'s. In fact, the highly praised 2001: A Space Odyssey, we never even see the advanced alien race that apparently planted large monoliths within our grasp. Or at least within grasp of our solar system.
For the seventies, George Lucas' Star Wars quite possibly introduced more types of differing aliens in that film alone than all the alien related films of this decade. Star Trek The Motion Picture had it's fair share of E.T.'s also.
And arguably the most visually iconic alien creature of all time is H.R. Giger's Alien creature, based from his earlier biomechanoid paintings. Not to mention, the superhero was added to the big blockbluster arena with the alien orphan from the planet Krypton, Superman.
Movie aliens had a thriving presence in the eighties, with the more famous being Spielberg's E.T., John Carpenter's The Thing, and John McTiernan's Predator. James Cameron took H.R. Giger's Alien to a new level by introducing the Queen alien.
And the Star Wars sequels brought along even more alien creatures with Yoda possibly the most popular of that film universe. The Alien franchise along with the Star Trek franchise continued the march of aliens in the nineties along with a few other films.
Certainly worth a mention is the menacing aliens of Independence Day and their weapons of mass destruction. While aggressive aliens of the nineties, including The Arrival and Starship Troopers, continued to thrive at the box office, there was also a fair share of comedic aliens such as Men in Black, Galaxy Quest, and Mars Attacks.
The new millennium so far has been like a sampler plate from benevolent to hostile aliens such as K-PAX and Signs. What appears to be missing from this current time period is a truly iconic alien to call it's own.
It's line up has been mainly already established star alien creatures via remakes, prequels, and sequels such as more Men in Black, The Thing, Alien vs. Predator, War of the Worlds, and others. A few exceptions would include James Cameron's Avatar, District 9, and John Carter.
Also, with so many of it's characters having alien origins, superhero movies, considered a sub-genre of sci-fi, has made a big impact at the box office. Recent articles around the web have been clamoring about the upcoming line up of sci-fi around the corner including the recently released Oblivion and Star Trek: Into the Darkness.
This second decade of the new millennium looks to be a strong period for sci-fi at the box office. We shall see if our beloved movie aliens take a sizeable role in what's to come.