a consolation prize for extinct species?

The dinosaurs of Jurassic Park (1993) by Steven Spielberg made an entire generation of children dream (and nightmare). Based on the eponymous novel by Michael Crichton (1942-2008) published in 1990, the film was a huge success upon its release. As Nicolas Deneschau recalls in his book Welcome to Jurassic Park: The Science of Cinema (Third Editions, 2022), “in less than three months, (he) will absolutely atomize all competition by accumulating nearly 500 million dollars on American territory”. The film owes its success in large part to its stars, dinosaurs cloned and cloistered on an island for a future amusement park. With the disastrous consequences that we know… From now on, “it becomes impossible to talk about the dangers of genetic manipulation without mentioning the park” writes Nicolas Deneschau. Besides, are we really capable of bringing extinct species back to life? And for what purpose? Forget the shirt in the pants and the hat of Professor Grant, and instead put on the white coat of Doctor Wu. Because to get answers, we will have to go behind the scenes of the genetics laboratories…

Cloning: not so simple!

Cloning as presented in Jurassic Park may seem disconcertingly simple. As we can read in Welcome to Jurassic Park” It’s necessary […] extract dinosaur blood from the mosquito, then implant the still living cells by mixing them with another contemporary frog DNA in an ostrich egg.” Of course, the method favored by geneticist Henry Wu is not without its limitations. Thus, the thick skin of dinosaurs should not have made them the preferred prey of mosquitoes. In addition, Nicolas Deneschau points out the fact that “the insect does not store blood, but digests it” and destroys it. But the main problem lies in the impossibility of recovering DNA from animals that died more than 66 million years ago.

The current state of cloning is based on the transfer of the nuclear genome of an individual into an oocyte which will develop in a closely related individual. “This technique is not yet fully developed for modern species, so for extinct species for which the probability of obtaining a 100% preserved genome is extremely low, the task promises to be monumental,” underlines Lionel Cavin, paleontologist and curator at the Natural History Museum of Geneva (Switzerland). He is the author, with the geneticist and evolutionary biologist Nadir Alvarez, of the work Bringing extinct species back to life? (Éditions Favre, 2022). After the first cases of cloned animals in the 1950s (leopard frogs), the first mammal was the famous Dolly sheep in 1996, who lived almost 7 years. Today, around thirty species of mammals have been cloned. But the only case concerning an extinct species is that of Celia, the last ibex of the Pyrenees killed by a falling tree in 2000. Three years later, cell nuclei from tissues taken from her in 1999 were implanted in domestic goat oocytes. Out of 285 embryos, only 54 are transferred to a surrogate mother, and none will reach beyond 2 months of gestation. A new experiment was carried out in 2009, this time with a full-term gestation. Unfortunately, the cloned lamb died a few minutes after birth due to a lung problem.

Rewilding the world with extinct species?

Cloning is not the only possible method for achieving the “de-extinction” of extinct species. A term that appeared recently and whose definition is still unclear. “Currently, it covers all the processes aimed at producing living beings corresponding to extinct organisms. This correspondence can range from simple physiological resemblance to the true “resurrection” of a species,” indicates Lionel Cavin. But why try to bring them back to life? “Although stopping the decline in biodiversity must necessarily involve the protection of species and their environment, it is not impossible to imagine going further than simple conservation by rewilding spaces. Nothing to do, however, with a zoo like Jurassic Park ! », replies the paleontologist. This idea consists of reintroducing or allowing the natural arrival of current animals that have disappeared from certain regions for centuries, or even millennia, to see them readapt there. Thus, camelids and cheetahs could return to North America, and lions roam the temperate and cold zones of Eurasia. These species play their ecological role in weakened ecosystems. However, their return could also lead to the return of old pathogens and new disease vectors, to name only these disadvantages.

“De-extinction” would help newcomers readjust more quickly to their old environment. Artificial selection thus promises to be able to find the characteristics of an extinct species (size, color) by crossing different varieties of descendants. Certain domestic oxen were selected in this way to resemble the aurochs, extinct in 1627. Same thing with plains zebras in order to obtain an animal resembling the couagga, extinct in 1883. Another possible route is that of genetic engineering. The complexity here lies in the ability to edit the genome using the molecular tool CRISPR-Cas9, enabling precision gene corrections. However, this system only aims to fill genomic gaps in specimens kept in museum collections. The reproduced animal will therefore only be an ersatz of the extinct species. Finally, the American paleontologist Jack Horner, who advised Spielberg on Jurassic Park, for its part defends the idea of ​​“de-evolution” and seeks to reappear the ancestral characteristics of a species by reactivating/deactivating certain of its genes. “The best known example is that of Chickenosaurus, consisting of finding in the chicken the genetic mechanisms responsible for the development of teeth, an elongated tail or a snout rather than a beak. According to the theory, we could arrive at an individual close to a small theropod dinosaur like Archeopteryx,” describes Lionel Cavin. But in practice, only embryos showed the beginnings of teeth or an unusual shape of the palate…

A stuffed specimen of Couagga (Equus quagga). Credits: MNHN/L. Bessol.

Protect, rewild and… cohabit?

In reality, “de-extinction” is far from being a miracle cure for the biodiversity crisis, and should certainly not be thought of as such. “It is not really considered for the myriad of small endangered species, such as insects, soil fauna, aquatic invertebrates… For them, we must naturally prioritize the protection of their environments,” recalls Lionel Cavin . But what about megafauna and its large species? The majority have already disappeared, and rewilding fueled by the rehabilitation of species close to extinct species could be of interest for the survival of ecosystems. However, this type of solution raises many ethical questions. “Of course, we must preserve African megafauna, but why not also ask regions that sheltered members of megafauna in the past to welcome their descendants? The possibility of such measurements lies first of all in our ability to live side by side with the wild world,” suggests the paleontologist. Cohabitation is often difficult, whether with bears and wolves in Europe, tigers in India or elephants in Botswana. The future will tell us if humanity has managed to make compromises between its tendency to domesticate the world and its desire for survival, both for itself and for the rest of current biodiversity…