In one of the many iconic scenes of Steven Spielberg’s Jurassic Park, Dr Alan Grant, stranded in a dinosaur enclosure discovers empty dinosaur eggshells. This is a surprise to everyone on the island as the scientists there had ensured them that all dinosaurs cloned were female, meaning that there was no males to reproduce. This was key to keeping the dinosaur population under control.
Ian Malcom, a sceptic, warned that anything is possible because “life finds a way”.
And he was right.
The Jurassic Park novel of 1990 was the inspiration for the film, written by a guy called Michael Crichton. Crichton wasn’t the most conventional author, having spent many years at medical school, which came after spending the first half of his life teaching Biology at the University of Cambridge. This gave him a good understanding of genetics (at least for the 1990s) which he could go on to use to create a ‘realistic’ science backbone for the novel’s storyline.
Whilst the visitors of the park are ensured all dinosaurs cloned are female, they are also told that to fill the missing gaps in the dinosaur genomes, the geneticists added frog, bird or lizard DNA. This adds an element of realism to the story, sequencing entire genomes of extinct animals using the technology of 1990 would have been a ridiculous suggestion, even for a film that resurrects dinosaurs.
The addition of the extra DNA supports a theory as to how females reproduced without a male. Parthenogenesis is a form of asexual reproduction that has been recorded in certain species, including certain types of frog, birds and lizards. In species capable of parthenogenesis, unfertilised eggs can, under the right conditions, still give rise to live young. Often, this will only happen when there isn’t a male around to sexually reproduce with, meaning the female dinosaurs were kept in the right conditions for this to happen.
One suggested explanation for why parthenogenesis exists is that it is a mechanism against extinction. This is as stranded females wouldn’t be able to reproduce unless they somehow find a male. Conveniently, parthenogenesis usually results in a male child, with which the mother can sexually reproduce with.
You also can’t rule out that dinosaurs already had the capability to carry out parthenogenesis. There is no current scientific evidence supporting this theory, although little is known about dinosaurs’ pasts.
What has surprised me is the level of unexplained scientific detail that runs through both the film and the novel. Great sections of the plot are held together by the key concepts of genetics, the only reason people know this is by filling in the gaps with their own knowledge. I think it is quite likely that Crichton intended parthenogenesis to be the answer to this riddle, but the fact nobody is certain is why Michael Crichton was a great novelist and screenwriter.