Michael Crichton’s book “Jurassic Park” served as a cautionary tale on scientists’ tampering with biology as they bring dinosaurs back to life without thinking about the consequences of their actions. When Steven Spielberg adapted it to the silver screen in what turned out to be a genuinely thrilling movie, much of it was changed and details were omitted to make it the kind of audience pleasing movie he was best known for making at the time. He doesn’t delve as much into the darker side of Crichton’s characters and made them more likable, and the changes proved impossible to miss.

Working with David Koepp, who got screenwriting credit along with Crichton, Spielberg developed the cartoon the main characters watch during the park tour to remove much of the exposition found in the book. Crichton goes into extensive detail about how dinosaurs were recreated using their DNA which ends up being found in mosquitoes trapped in fossilized tree resin. Despite many scientists saying it is impossible to create dinosaurs in this way, it still makes for a very compelling story.

Koepp also cut out a sequence from the book which had Grant and Hammond’s grandchildren being chased down the river by the Tyrannosaurus. This was done for budgetary reasons, but this dinosaur would later appear in “Jurassic Park III.”

The book also had a sub-plot about young children getting attacked by small theropod dinosaurs, but Spielberg cut this out because he found it too horrific. However, that same sub-plot would be used to start off the movie version of “Jurassic Park: The Lost World.”

When it came to the characters, some of the biggest changes occurred with John Hammond, the curator of Jurassic Park. The book describes him as a ruthless businessman who is arrogant, deceptive, utterly disrespectful, and thoughtlessly rude. Even though he eventually comes to see the consequences of his experiments, he still moves ahead with his plans in the name of profit. He is even willing to sacrifice his grandchildren to the dinosaurs if that’s what it takes.

In the movie where Hammond is portrayed by Sir Richard Attenborough, he is instead an eccentric and friendly old man who is caught up in the wonder of what he has helped bring to life. However, he eventually realizes he cannot control the dinosaurs and is desperate to see his grandchildren brought back safely. This change came about because Spielberg very much related to Hammond’s obsession with showmanship.

Dr. Alan Grant, played by Sam Neil, is shown to like kids and enjoys being around them in the book. However, the movie has him being not the least bit fond of them. This change was made to give Grant more room for character development as he comes to be the father figure Hammond’s grandchildren lack when things go wrong.

Ellie Sattler, played by Laura Dern, is described as a 23-year old graduate student of Grant’s who is planning to get married to someone other than him. In the movie, she is Grant’s love interest and hopes he will one day be open to having children with her.

Jeff Goldblum gave a scene stealing performance as chaos theorist Ian Malcolm, and he gives Spielberg’s film the bulk of its comic relief. Crichton, however, wrote Malcolm as being more serious, philosophical, and at times downright condescending. Unlike the movie, Malcolm is killed off at the end of the book, but in the follow-up book “The Lost World” he is revealed to have survived.

One character that got drastically downsized was Dr. Henry Wu who is played by B.D. Wong. Crichton has him providing much of the detail about how the dinosaurs are cloned, and he stays on the island and is eventually killed off while the movie has him heading off to the mainland where he survives, and he was the only actor from this movie to appear in “Jurassic World.”

The lawyer Donald Gennaro, one of the movie’s greediest and thoughtless characters, comes across as rather likable in the way Crichton writes him. While he becomes something of a scapegoat towards the end, he is the one most insistent on the island being destroyed to protect the rest of the world from these dinosaurs. But in the movie, he is ever so eager to exploit the park’s profit potential any which way he can.

Then there are Hammond’s grandchildren, Lex and Tim, who are along for the tour of the island as well. In the book, Tim is the oldest of two at 11 years old and is good with computers while Lex is only 7 and more into sports. Spielberg switched these characters around to where Lex was the oldest, and he did this in order to cast Joseph Mazzello as Tim. Ariana Richards plays Lex, and she’s the more into computers and helps save the main characters in one critical scene.

Looking back at “Jurassic Park” the movie, it was the last time Spielberg adapted a book and changed the characters to where they were likable and easier for audiences to spend time with. His next movie was “Schindler’s List” which had him exploring one of the darkest periods of human history, and making it had a major effect on the movies he directed afterwards. When it came to turning “The Lost World” into a movie, Spielberg was more willing to embrace the darker aspects Crichton explored intensely in his books, and this was something readers wished he had done with the first movie.