Twenty-two years after the events of Jurassic Park, Isla Nublar, an islet located off Central America's Pacific Coast, near Costa Rica, now features a fully functioning dinosaur theme park, Jurassic World, as originally envisioned by John Hammond. This new park is owned by the Masrani Global Corporation. Owen Grady (Chris Pratt), a member of the park's on-site staff, conducts behavioral research on the velociraptors. At the corporation's request, the park's geneticists create the Indominus Rex, a genetically modified hybrid dinosaur, to boost visitor attendance, but it soon breaks loose and runs wild throughout the park, forcing the staff to consider unique measures to stop it.
In March 2001, Jurassic Park III director Joe Johnston denied rumors of a fourth film. Late in Jurassic Park III 's production, executive producer Steven Spielberg devised a story idea for a fourth film. He wished the idea had been used for the third film instead. In June 2001, Johnston said he would not direct the film, and that Spielberg had a story idea that would take the series' mythology to a new level. Johnston later said the film would feel like a departure from previous films, implying it would not be set on an island. In July 2001, actor Sam Neill, who portrayed Dr. Alan Grant in previous films, said he could not imagine a way for his character to be involved in another film. That same month, Johnston denied, then later hinted, that the film would involve the Pteranodons from the ending of Jurassic Park III.
In April 2002, it was reported that the film would be the last one in the series, and would ignore its predecessor's events. In a June 2002 interview with Starlog magazine, Steven Spielberg officially confirmed the fourth film, which he hoped to have Joe Johnston direct. Spielberg confirmed there was a story which he considered to be the best one since the first film. On November 4, 2002, Sam Neill said there was a chance he would be in the film. On November 7, 2002, William Monahan was announced as screenwriter, with Spielberg as executive producer and Kathleen Kennedy as producer. A month later, the film was announced for a summer 2005 release.
In January 2003, Jeff Goldblum said he had been asked to stay available for a possible return of his character Ian Malcolm. On January 30, 2003, it was reported that the story would involve dinosaurs migrating to the Costa Rican mainland. A team of experts, including Alan Grant and Ian Malcolm, chart an expedition to one of InGen's offshore islands and discover the dinosaurs breeding uncontrollablly. In April 2003, Stan Winston confirmed his special-effects studio was in the design phase for the film. Winston also said that Spielberg wanted to adapt several previously unfilmed scenes from Michael Crichton's Jurassic Park novels. In July 2003, Keira Knightley said she was in consideration for two separate roles, including a small role as a granddaughter. Monahan's first draft of the script was finished later that month, with a story no longer set in the jungle as in previous films. A director had yet to be discussed at that time. Sam Neill confirmed he would reprise his character, with filming set to begin in 2004 in California and Hawaii.
In September 2003, Richard Attenborough said he would reprise his role as John Hammond. In October 2003, paleontologist Jack Horner said he would return as technical adviser for the fourth film as he had done for previous Jurassic Park films. Horner hinted that Velociraptors would be an integral part of the film. Keira Knightley's character was written out in late 2003. In March 2004, Joe Johnston said he had not been asked to direct the film, and hoped that Steven Spielberg would direct it. Johnston said a story was being written that would take the series in a completely different direction "away from the island and away from the T-Rex and all this." In May 2004, it was reported that screenwriter John Sayles was writing the script. Sayles was hired to finish earlier work done by Monahan, who had left the project to work on Kingdom of Heaven. By June 2004, Frank Marshall had joined the project as a producer.
In June 2004, it was reported that Alex Proyas was in discussions to direct, with filming expected to begin in March 2005 for a re-scheduled winter 2005 release. Filming would have started at Pinewood Studios, where a massive tank was to be constructed for scenes involving marine reptiles. In July 2004, the script was being rewritten, with Jeremy Piven and Emmy Rossum being considered for two of the lead roles and Richard Attenborough reprising his character. Later that month, Proyas said he was not interested in directing the film.
In August 2004, Aint It Cool News published a review of a leaked draft of the film's script. The story would have involved a new character, a mercenary named Nick Harris, who is hired by a Swiss corporation and put in charge of training a team of five genetically-modified Deinonychus for use in rescue missions. John Hammond would be the only returning character in this draft. In 2005, John Sayles confirmed this to be an early draft of the script, intercepted through Steven Spielberg's email by a hacker.
In late August 2004, David Boreanaz was rumored and later reported to have the lead role. Boreanaz was actually in consideration for Fantastic Four. Sayles was still re-writing the script in September 2004, with the film on track for a winter 2005 release. Sayles' next draft, which involved genetically engineered human-dinosaur mercenaries, was scrapped.
In April 2005, Stan Winston confirmed the film was on hold due to repeated revisions of the film's script, none of which satisfied Spielberg. According to Winston, "He felt neither of [the drafts] balanced the science and adventure elements effectively. It's a tough compromise to reach, as too much science will make the movie too talky, but too much adventure will make it seem hollow." In November 2005, Spielberg said he planned to include a scene in the film (taken from the novel, The Lost World) that would involve characters on motorcycles outrunning raptors.
In January 2006, Joe Johnston and Jack Horner were working on a new screenplay, with more work on it expected to begin immediately after the 2008 release of Indiana Jones and the Kingdom of the Crystal Skull. In February 2006, Frank Marshall said the film now had a good script, with filming expected to begin in 2007 for a 2008 release. In March 2006, Marshall said the film had a script and was getting a director, with Johnston as a possible candidate. In April 2006, Marshall said there was an idea for the film, but not a script. Marshall went on to deny that Michael Crichton would write the script, or that Steven Spielberg would direct it. The script was still being worked on in June 2006.
