The massive, extinct marine reptile known as the Mosasaurus has captured the public imagination, largely due to its fearsome portrayal in popular films. This creature was an apex predator that dominated the world’s oceans during the Late Cretaceous period, disappearing over 66 million years ago with the non-avian dinosaurs. While the concept of resurrecting such a spectacular animal is compelling, the short answer to whether scientists are trying to bring back the Mosasaurus is no. Current de-extinction efforts are highly focused on species that went extinct far more recently, mainly due to the fundamental biological limitations imposed by the passage of deep time.
The Critical Barrier to Bringing Back the Mosasaurus
The primary obstacle preventing the resurrection of the Mosasaurus is the severe degradation of genetic material over immense timescales. Deoxyribonucleic acid, or DNA, is surprisingly fragile and breaks down after an organism dies. Scientists estimate that DNA has a half-life of approximately 521 years under ideal preservation conditions, such as those found in bone.
This half-life means that half of the chemical bonds in a DNA sample will be broken after 521 years, and half of the remaining bonds will be gone after another 521 years. Given that the Mosasaurus vanished around 66 million years ago, all retrievable chemical bonds in its DNA would have been completely destroyed long ago, even if perfectly fossilized.
The maximum limit for retrieving fragments of DNA long enough to be sequenced is thought to be around one million years, and only under conditions of perpetual freezing. This is why the focus of de-extinction is on creatures from the Pleistocene epoch, such as the Woolly Mammoth, whose remains are relatively recent and often preserved in permafrost. The genetic material of the Mosasaurus is too old, existing only as fossilized bone and not as viable genetic fragments.
Current Targets of De-Extinction Efforts
Instead of attempting the impossible with creatures from the age of dinosaurs, scientists are concentrating on species that have been extinct for a much shorter duration, typically within the last 50,000 years. These efforts target animals whose genetic material is available in a fragmented but recoverable state. The common thread among these target species is their relatively recent extinction and the availability of sufficiently preserved genetic samples, often from frozen tissues or museum specimens.
Prominent candidates for de-extinction include:
- The Woolly Mammoth, which went extinct around 4,000 years ago, with many frozen remains containing usable DNA fragments.
- The Tasmanian Tiger (Thylacine), a carnivorous marsupial that only went extinct in the 1930s.
- The Passenger Pigeon, whose last individual died in 1914, due to the availability of well-preserved museum specimens.
- The Pyrenean Ibex (bucardo), which was the first animal to be briefly “de-extincted” through cloning in 2003.
- Projects targeting the Dodo and the Aurochs, an extinct wild ox, which rely on genetic data from the last few centuries or millennia.
The goal of these projects is often to restore lost ecological functions rather than creating a biological duplicate.
The Scientific Methods Used in De-Extinction
De-extinction relies on sophisticated genetic and reproductive technologies to bring back an approximation of an extinct species, often resulting in a hybrid or proxy organism.
Gene Editing
This approach utilizes tools like CRISPR-Cas9 to modify the genome of a closely related living species. For example, researchers are editing the DNA of the Asian elephant to insert genes for cold resistance and hair length, creating an animal with traits similar to the Woolly Mammoth.
This process involves sequencing the fragmented DNA of the extinct species to identify the traits that made it unique. Scientists then use the CRISPR system, which acts as a pair of molecular scissors, to precisely cut and paste these extinct traits into the genome of the closest living relative. The result is a genetically engineered cell line that carries the desired characteristics of the extinct animal.
Cloning
The second primary method is Cloning, specifically Somatic Cell Nuclear Transfer (SCNT), the technique used to create Dolly the sheep. SCNT involves taking the nucleus, which contains the genetic material, from a somatic cell of the extinct species and inserting it into an egg cell of a living relative that has had its own nucleus removed. This reconstructed egg is then stimulated to start dividing and is implanted into a surrogate mother of the related living species.
SCNT requires near-intact genetic material, making it feasible only for very recently extinct species or those with cryopreserved cells, though it is often combined with gene editing to create a viable embryo.
Back-Breeding
A less technology-intensive method, used for species like the Quagga and the Aurochs, is Back-Breeding. This involves selectively breeding living descendants, such as modern domestic cattle, to amplify ancestral traits that still exist within the population’s genetic code. This method aims to recreate the appearance and behavior of the extinct species through careful, guided selection over generations.
The Ecological and Ethical Debate
Beyond the technical challenges, de-extinction efforts are subject to significant ecological and ethical debate concerning their potential impact on conservation. A primary ecological concern is the introduction of a new or genetically modified species into an ecosystem that has changed drastically since its extinction. The re-introduced animal may not have a suitable habitat, or it might become an invasive species, potentially disrupting the existing food web and negatively affecting current species.
There are also practical arguments that question the allocation of financial resources. De-extinction is an expensive endeavor, and some critics suggest that the millions of dollars spent on reviving a few lost species could be better used to protect the hundreds of species currently facing extinction. This debate centers on whether the focus should be on undoing past mistakes or on preventing future losses.
Ethical considerations also revolve around the welfare of the animals involved, particularly the surrogate mothers. The process of SCNT and gestation in a surrogate of a related species can be difficult, often resulting in high rates of miscarriage and birth defects. Some question the philosophical implications of creating a new animal for a world that may no longer be able to sustain it, arguing that such efforts constitute “playing God” with nature.