Biological issues in Jurassic Park


Biological issues in Jurassic Park

"Jurassic Park", a book by Michael Crichton, with a film version directed by Steven Spielberg, revolves around the resurrection of dinosaurs via genetic engineering. Scientists and enthusiasts have brought up a number of issues with facts and feasibility.

Halfway through the original text, characters John Hammond and Henry Wu have a discussion. Wu says that they could and should make better dinosaurs. Hammond scoffs at the idea, saying that they have real dinosaurs; who would want more? Wu's reply is that they should not bother with reality because the people coming to see Jurassic Park do not want reality, they want their expectations.

Many of the dinosaur species depicted in the film did not actually live in the Jurassic Period, but in the following Cretaceous Period.

Dinosaurs

"Velociraptor"

The raptors in the novel, following through to the film raptors, were larger than the species going by the name because during the writing of the novel, a previously discovered dinosaur named "Deinonychus" (closely related to "Velociraptor", but larger) was interpreted as a "Velociraptor" species by some scientists, notably Gregory S. Paul.cite_book |last=Paul |first=Gregory S. |authorlink=Gregory S. Paul |year=1988 |title=Predatory Dinosaurs of the World |location=New York |publisher=Simon and Schuster |pages=464pp |isbn=978-0671619466] Crichton wrote his novel based on the idea of a human sized raptor, but after the publication—when the movie was already in production—the idea of "Deinonychus" being a "Velociraptor" species was dropped.

During the movie's production, the effects supervisors acknowledged that the "Velociraptor" featured in the movie were sized identically to the larger "Deinonychus". However, during the filming paleontologists came across a larger dromaeosaurid species named "Utahraptor" and the larger raptors remained, even though "Utahraptor" was substantially larger (21 feet long) than the movie's raptors. It should be noted, also, that at the start of the film a "Velociraptor" skeleton is uncovered in Montana - no examples of the dinosaur have been uncovered in the USA (although both "Deinonychus" and "Utahraptor" are American dinosaurs). The fossil skeleton is similarly inaccurately large. It is possible that the velociraptors in the movie are re-classified "Deinonychus", though in the book they are said to be "Velociraptor mongoliensis".

The high intelligence of the film's "Velociraptor" is considered somewhat unlikely by scientists, given the relative size of their brains and comparisons with modern animals.cite_journal |last=Larson |first=Hans C.E. |coauthors=Sereno, Paul C.; & Wilson, Jeffrey A. |year=2000 |title=Forebrain enlargement among nonavian theropod dinosaurs |journal=Journal of Vertebrate Paleontology |volume=20 |issue=3 |pages=615–618 |url=http://vertpaleo.org/publications/jvp/contents-20-3.cfm |doi=10.1671/0272-4634(2000)020 [0615:FEANTD] 2.0.CO;2 |doilabel=10.1671/0272-4634(2000)020[0615:FEANTD]2.0.CO;2]

It is certain that "Velociraptor" had feathers.cite journal |last=Turner |first=A.H. |coauthors=Makovicky, P.J.; Norell, M.A. |year=2007 |title=Feather quill knobs in the dinosaur "Velociraptor" |journal=Science |volume=317 |issue=5845 |pages=1721|doi=10.1126/science.1145076 |url=http://www.sciencemag.org/cgi/reprint/317/5845/1721.pdf |format=pdf] Neither the film nor the novel dinosaurs had feathers; however, both were created before the discovery of feathered dinosaurs closely related to "Velociraptor" (e.g. "Microraptor").cite_journal |last=Xu Xing |authorlink=Xu Xing |coauthors=Zhou Zhonghe, Wang Xiaolin, Kuang Xuewen, Zhang Fucheng & Du Xiangke |year=2003 |title=Four-winged dinosaurs from China |journal=Nature |issue=421 |pages=335–340 |doi=10.1038/nature01342] cite_book |last=Paul |first=Gregory S. |authorlink=Gregory S. Paul |year=2002 |title=Dinosaurs of the Air: The Evolution and Loss of Flight in Dinosaurs and Birds |location=Baltimore |publisher=Johns Hopkins University Press |pages=472pp |isbn=978-0801867637] In "Jurassic Park III" the raptor was remodelled and small feathers on the males' heads were included, while still looking similar to the original design.

As with other bipedal dinosaurs in the films, the hands of "Velociraptor" are depicted with the palms facing down and backwards, but this would have been anatomically impossible for the real animals, as their forearm bones (ulna and radius) could not rotate in this way. Instead, their palms would have faced each other, like a person about to applaud.

"Procompsognathus"

The "Procompsognathus" are given several attributes in the novels that cannot be determined from the fossil evidence to date. They are presented as living and hunting in large groups; as scavengers and coprophagists (eaters of feces), useful in keeping the park clean of sauropod excrement; and as secreting a venom described as similar to that of a cobra, although more primitive. This ability to incapacitate their prey is absent in the films, where they are dropped in favour of "Compsognathus".

In reality, "Procompsognathus" is known from a single partial skeleton from the Late Triassic of Germany, with a partial skull that may belong to it or, more likely, an early relative of modern crocodilians.cite book|chapter=Procompsognathus |last=Glut |first=Donald F. |authorlink=Donald F. Glut |title=Dinosaurs: The Encyclopedia |year=1997 |publisher=McFarland & Co |location=Jefferson, North Carolina |pages=729–731 |isbn=0-89950-917-7] cite book |last=Tykoski |first=Ronald B. |coauthors=and Rowe, Timothy |year=2004 |chapter=Ceratosauria |editor=Weishampel, David B.; Dodson, Peter; and Osmólska, Halszka (eds.) |title=The Dinosauria |edition=Second Edition |publisher=University of California Press |location=Berkeley |pages=47–70 |isbn=0-520-24209-2] Because only one individual is known, there is no direct evidence that it lived in groups; however, related animals such as "Coelophysis" and "Megapnosaurus" have been found in groups of numerous individuals, such as at Ghost Ranch. As there are no uncontroversial remains of the head of "Procomposognathus", its diet cannot be inferred from the form of its teeth and jaws; other coelophysoids are seen as carnivores with skull adaptations that may have been advantageous when handling small prey. Finally, aside from a possible theropod tooth from the Late Cretaceous of Baja California with grooving similar to that found on the teeth of venomous snakes and lizards,cite web |last=Hecht |first=Jeff |title=Re: Venomous Therapsid |url=http://dml.cmnh.org/2002Aug/msg00551.html |work=The Dinosaur Mailing List (contains a copy of a draft of material author Hecht wrote for New Scientist regarding 2000 abstract and reaction)] there is no evidence for venom secretion in dinosaurs, and scientists consider it unlikely.Fact|date=September 2007

"Dilophosaurus"

The movie "Dilophosaurus" stands about 1.2 meters (4 ft) tall,, while its real-life counterparts measured on the order of 6 meters (20 ft) long and 1.4 meters (4.5 ft) tall at the hips.cite book |last=Paul |first=Gregory S. |title=Predatory Dinosaurs of the World |year=1988 |publisher=Simon & Schuster |location=New York |isbn=0-671-61946-2 |chapter=Genus "Dilophosaurus" |pages=pp. 268-270 ] According to a "Making-of" book this was a deliberate deviation from accuracy for stylistic purposes, and to differentiate it from the "Velociraptors".cite book |last=Shay |first=Don |coauthors=Jody Duncan |title=The making of Jurassic Park |year=1993 |publisher=Ballantine Books |pages=pp. 35-36 |isbn=1852837748] It also has a totally speculative frill like the Australian frill-necked lizard. The "Dilophosaurus" shown in the film could be considered a juvenile, based upon Nedry's remark that he's glad not to have run into one of its "big brothers" (Jurassic Park Legacy also considers this). The novel's version is full-sized and lacks the frill. Both depictions of the dinosaur eject a potent, blinding venom in both their bite and their spit, like a spitting cobra, and use it to hunt; the novel hints that this is not suggested by fossil evidence.cite book |last=Crichton |first=Michael |authorlink=Michael Crichton |title=Jurassic Park |year=1990 |publisher=Alfred A. Knopf |isbn=0-394-58816-9 |quote=It was Muldoon's view that some dinosaurs were too dangerous to be kept in a park setting. In part, the danger existed because they still knew so little about the animals. For example, nobody even suspected the dilophosaurs were poisonous until they were observed hunting indigenous rats on the island—biting the rodents and then stepping back, to wait for them to die. And even then nobody suspected the dilophosaurs could spit until one of the handlers was almost blinded by spitting venom.]

"Brachiosaurus"

The "Brachiosaurus" in the movie is shown to be chewing its food with a side to side motion of its lower jaw. In reality, it could not feed like this. Brachiosaurid skulls and jaws were limited to up and down motions, and their teeth were specialized for shearing and cropping plant material. Other sauropods, such as diplodocoids, could move their jaws backward and forward, but were probably using this motion to strip branches, not to chew plants.cite book |last=Barrett |first=Paul M. |coauthors=and Upchurch, Paul |year=2005 |chapter=Sauropodomorph diversity through time |title=The Sauropods: Evolution and Paleobiology |editors=Curry Rogers, Kristina A.; and Wilson, Jeffrey A. |pages=125-156 |publisher=University of California |location=Berkeley, CA |isbn=0-520-24623-3] Instead of processing food in the mouth, sauropods probably relied on taking in as much food as possible and processing it farther down the digestive tract, either through gastroliths (rocks swallowed and used for grinding in a gizzard-like organ; note however that this hypothesis, while common in the popular literature, is now considered unlikely in sauropods), [cite journal|author=Wings O|title=A review of gastrolith function with implications for fossil vertebrates and a revised classification|journal=Palaeontologica Polonica|volume=52|issue=1|pages=1–16|year=2007|url=http://www.app.pan.pl/acta52/app52-001.pdf|accessdate=2007-11-24|format=PDF] or simply by digestion through fermentation by microorganisms.cite book |last=Carpenter |first=Kenneth |authorlink=Kenneth Carpenter |year=2006 |chapter=Biggest of the big: a critical re-evaluation of the mega-sauropod "Amphicoelias fragillimus" |editor=Foster, John R.; and Lucas, Spencer G. (eds.) |title=Paleontology and Geology of the Upper Jurassic Morrison Formation |publisher=New Mexico Museum of Natural History and Science |location=Albuquerque |series=New Mexico Museum of Natural History and Science Bulletin 36 |pages=131-138 |url=https://scientists.dmns.org/sites/kencarpenter/PDFs%20of%20publications/Amphicoelias.pdf |format=pdf]

Additionally, the "Brachiosaurus" head is shown much larger than its actual size in an up-close shot when Dr. Alan Grant, Tim Murphy and Alexis Murphy try to feed it. In the other shots of "Brachiosaurus" the head size is proportionate to the body.

"Tyrannosaurus"

The movie's theory is that the "Tyrannosaurus rex" would be unable to see someone if they were to remain still (this was explained in the novel as being another side effect of the splicing of frog DNA with that of the dinosaurs); however, evidence has shown "T. rex" to have had high visual acuity and binocular vision. [Stevens, K.A. (2006) Binocular vision in theropod dinosaurs. Journal of Vertebrate Paleontology 26(2):321–330] Some argue that it would still be able to smell them regardless. [cite news | first=Eric | last=Jaffe | coauthors= | title=Sight for 'Saur Eyes: T. rex vision was among nature's best | date= | publisher= | url =http://www.sciencenews.org/articles/20060701/fob2.asp | work =Science News | pages = | accessdate = 2007-10-02 | language = ] In the sequel novel, "The Lost World", it is suggested that the "Tyrannosaurus" can in fact see inanimate objects, and was actually not hungry. In fact, a character who specifically attempted this technique dies when the "T. rex" nudges him to see if he was there as Malcolm mentions that he was listening to "the wrong scientists."Carpenter, K. & Smith, M.B. 2001. Forelimb osteology and biomechanics of "Tyrannosaurus". In: Tanke, D.H. & Carpenter, K. (Eds.). "Mesozoic Vertebrate Life". Bloomington: Indiana University Press. Pp. 90-116. (download [https://scientists.dmns.org/sites/kencarpenter/PDFs%20of%20publications/pdfs.aspx here] )] Derstler, K., and Miller, M.M. (2007). "Anatomy and function of digit III of the "Tyrannosaurus rex" manus." Geological Society of America "Abstracts with Programs", 39(6): 77. [http://gsa.confex.com/gsa/2007AM/finalprogram/abstract_132345.htm Abstract] .]

"Tyrannosaurus" is also shown as being able to keep pace with a jeep travelling at considerable speed; it is debated within the palaeontological community whether a "T. rex" could even achieve this speed, much less maintain it. [Levy, Dawn (February 27, 2002) [http://news-service.stanford.edu/news/2002/march6/tyrannowalk-36.html T. rex's new
] , "stanford.edu"
] Anatomically, its short forelimbs would be unable to cushion an impact if it were to fall at speed; this could be fatal. Animators at Industrial Light & Magic were forced to use optical illusions in order to make the computer-generated "Tyrannosaurus" appear to convincingly 'run' at that speed.Hutchinson, J. R. and Garcia, M. (2002). Tyrannosaurus was not a fast runner. "Nature" 415: 1018-1021]

"Spinosaurus"

The "Spinosaurus" in "Jurassic Park 3" was shorter than the real animal. Also, its teeth are very straight, conical and crocodilian in reality; but they are hooked and serrated in the movie. Finally, although "Spinosaurus" forelimbs have never been found, the wrists of closely related animals such as "Baryonyx"; and of theropods in general, show that "Spinosaurus" could not move its hands like it did to break the neck of a "Tyrannosaurus".

"Pachycephalosaurus"

The "Pachycephalosaurus" in ' was downsized. In ', the dinosaur was of correct size.

"Stegosaurus"

The "Stegosaurus" in "" was almost twice the size of the real animal. It seems to be downsized to correct size in "Jurassic Park: Operation Genesis".

Other reptiles

"Pterosaurs"

Like the "Cearadactylus" in the novel, the "Pteranodon" in "Jurassic Park III" is interpreted as aggressive and able to pick a teenager up with its feet (a similar scene was planned for the climax of ', but omitted after palaeontological advisors on the production declared that this would not have been possible). However, both pterosaur genera were thought to have eaten fish,cite book |last=Wellnhofer |first=Peter |publisher=Salamander Books Ltd |ISBN=0861015665 |year=1991 |title=The Illustrated Encyclopedia of Pterosaurs |pages=p. 159 |quote="They [known pterosaurs] fed on aquatic organisms. ... Fossilized stomach contents of some pterosaurs such as... "Pteranodon", have been found, these being the remains of the last meal before they died. In all cases they are remains of fish."] and were incapable of grasping with their feet. In reality it is unlikely a Pterosaur of any kind would have either the strength or motive to lift up a person. Also, despite the fact that the name "Pteranodon" means 'winged without teeth' or 'winged toothless"", the "Pteranodon" in "Jurassic Park 3" have small sharp teeth in their bills.

Other issues

In the scene where a baby dinosaur hatches from an egg in the laboratory, Dr. Grant asks Dr. Wu, "What species is this?" Dr. Wu replies, "It's a "Velociraptor"." This is not strictly accurate: "Velociraptor", by itself, is the genus, not the species, as it would need the specific descriptor "mongoliensis" appended to give the species name, in full, "Velociraptor mongoliensis" (or, if the raptors were "Deinonychus", "Deinonychus antirrhopus").

A similar issue occurs in the restaurant scene in the movie, in which Dr. Grant describes dinosaurs and man as "two species". There are about 700 identified species of dinosaur, not including birds.

Biotechnological background

The dinosaur DNA is extracted from fossilized mosquitoes, and this small amount is then amplified by polymerase chain reaction (PCR). This has been done before, for example with a Cretaceous weevil in Cano "et al." (1993) (no dinosaur DNA was found).

There are some problems with this approach:
*The DNA featured in the movie comes from a Dominican amber mine, though this mine is never stated to be the sole source. The novel indicates sources are global as Hammond's widespread purchasing and stockpiling of amber comes under scrutiny. Dominican amber is 10 million years to 30 million years old,George Poinar, Jr. and Roberta Poinar, 1999. "The Amber Forest: A Reconstruction of a Vanished World", (Princeton University Press)] when dinosaurs died out 65 million years ago.
* None of the dinosaurs featured in the movie are known to have existed in the Dominican Republic 65 million years ago (though, again, whether that mine is the only source for DNA is unknown).
* The mosquito had to have had just one species of dinosaur as its food source to avoid a mix-up.
* The scene featuring a close-up of the mosquito clearly shows fuzzy antennae, meaning the particular insect is male. Only female mosquitoes, however, suck blood.
* It is unknown which dinosaur the sample contains. It would be impossible to tell which species it is, because the DNA sequences would fit somewhere between that of birds and crocodiles. The book does address this, stating that they "just grow it and find out", to mathematician and chaos theorist Ian Malcolm's annoyance.
* The dinosaur DNA has to be correct (it has to contain every chromosome) and should contain no sequence gaps. The book and movie did address this issue, however, and had the scientists use frog DNA to compensate for the gaps in the dinosaur DNA. However, this causes a problem, as the dinosaurs are then able to change sex (as the frogs from which the DNA was obtained were able to do) and reproduce, thus furthering the problems leading to the park's collapse.
* The DNA is mixed with mosquito, bacterial, and viral DNA. Although PCR is very specific, it is sensitive to contamination, and if the wrong primers are used, it will also amplify the other DNA.
* Because DNA is broken down by nucleases in the mosquito gut, the mosquito would have to be preserved immediately after feeding; this would be problematic for the park's scientists, although it would explain the lack of mass contamination in the individual samples.

Furthermore, in the fossilization process, molecules are altered. Nevertheless, amber is the best preservative, because organic material is preserved. But DNA cannot survive completely without gaps for tens or hundreds of millions of years.

Tens of thousands of DNA base pairs were recently sequenced from 40,000-year-old skeletal remains of cave bears without using PCR, establishing that, in principle, large-scale genomic sequencing of fossilized remains is possible. Of course, the remains used in this study are orders of magnitude younger than anything from the dinosaur era, and the technique might not extend to those creatures.

In the book the gaps in the DNA are filled by hybridizing the DNA with either bird, lizard, or frog DNA. In the movie, only frog DNA is used. This is extremely difficult, as one would need to know which dinosaur genes are homologous with frog genes. The use of frog genes was a plot device, to allow some females to change sex and breed nevertheless (although natural sex change is also possible in some more advanced vertebrates).

The dinosaurs were genetically altered so they could not produce lysine, forcing them to depend on lysine supplements provided by the park's veterinary staff. Most vertebrates cannot produce lysine by default as it is an essential amino acid.

The movie states that all dinosaurs are female because all vertebrate embryos are inherently female, requiring an extra hormone at the right phase to make them male. This is not technically true. Vertebrate embryos are undifferentiated, possessing organs that can grow into either male or female reproductive systems. In mammals, at a certain developmental stage the Y chromosome triggers a flood of testosterone, causing the fetus to develop into a male. If, for some reason this doesn't happen, the fetus will develop as an XY Female (See Swyer syndrome). Birds and reptiles (and presumably, dinosaurs) don't use Y Chromosomes in this way. In fact, they seem to use an opposite system with females possessing a W chromosome and a Z chromosome and males possessing two Z Chromosomes. In the scenario presented in Jurassic Park, it seems likely that all the dinosaurs in the park would have been functional males or sterile males possessing an extra chromosome (See Hermaphrodite).

The next step would be bringing the DNA strands to expression. For that, one would need to inject the dinosaur DNA into the nucleus of a fertilized egg cell of a close relative of dinosaurs (birds or crocodiles, not frogs). This technique is based on reproductive cloning, which was used to clone Dolly. In the movie, ostrich eggs are used for this purpose. However, the development of an embryo is regulated by hormones in the egg/uterus and the environment. These (bird or crocodilian) hormones need to have the same effect as their original dinosaurian counterparts. For that, they have to be able to recognize particular pieces of dinosaur DNA, a currently impossible task. New research in plastics, however, has allowed for the creation of synthetic eggs such as those that were used in the book.Fact|date=December 2007 In the book Henry Wu claims that egg yolk is nothing but a growth medium that can be created in a laboratory. However, if it were this simple, an embryo could just be put into such a medium and left to grow (a scene in the third movie seems to show that some embryos were placed in tanks and that the scientists achieved some success because the embryos did grow big enough to be visibleFact|date=June 2008). Extra hormones are needed from the original parent specimen, however, or constructed precisely from using the genome in order for the embryo to flourish.

References

* Cano R.J., Poinar H.N., Pieniazek N.J., Acra A., Poinar G.O. Jr. (1993). [http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?holding=npg&cmd=Retrieve&db=PubMed&list_uids=8505978&dopt=Abstract Amplification and Sequencing of DNA from a 120–135-Million-Year-Old Weevil] . "Nature", 363:536–538
* Weaver, R. F. (2002). "Molecular Biology". McGraw-Hill, New York, p. 76. ISBN 0-07-234517-9
* Noonan, J.P., "et al." [http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=15933159&query_hl=4 Genomic sequencing of Pleistocene cave bears] . "Science" 309(5734):597–599, July 2005.
*cite book| title= The Science of Jurassic Park and The Lost World Or, How to build a Dinosaur| last=DeSalle | first= Rob| coauthors= Lindly, David| year= 1997| publishers= Basic Books |location= New York| isbn= 0-465-07379-4|pages= pp 1-194

Further reading

* "The Science of Jurassic Park and The Lost World. Or How to Build a Dinosaur." Rob DeSalle and David Lindley. BasicBooks, New York, 1997. ISBN 0-465-07379-4.


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