There are no solid facts as to the origins of the Xenomorph species ; instead, there are many theories which cannot be confirmed. They may be an artificially created species, or they may have evolved naturally on a planet very different than our own.
Aside from their repeated conflicts with humans , Xenomorphs have notably been associated with the Yautja (Predators) , leading to the extensive Alien vs. Predator franchise , including the films Alien vs. Predator ( 2004 ) and Aliens vs. Predator: Requiem ( 2007 ). The Xenomorph has also featured heavily in numerous literature and video game spin-offs, including crossovers with other well-known franchises.
The Alien design is credited to Swiss surrealist and artist H. R. Giger , originating in a lithograph titled Necronom IV and refined for the series' first film, Alien . The practical effects for the Alien's head were designed and constructed by Italian special effects designer Carlo Rambaldi . The species' design and life cycle have been extensively augmented, sometimes inconsistently, throughout each film.