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The biological limits of de-extinction

Q: Can science bring back Dinosaurs to life?

Krishna:

Image credit: Orla of Getty Images

Bringing the exact extinct species back to life is not possible at present, say scientists.

Advances in biotechnology, including ancient DNA sequencing, genome analysis and gene editing, have led some to believe that it may be possible to bring extinct species back to life.

De-extinction—the effort to resurrect extinct species using biotechnology—faces severe biological, genetic, and ecological limits. Rather than creating an exact copy of a lost species, current methods yield modern ecological proxies or hybrids.

The reasons are

1. Genomic incompleteness and degradation

Ancient DNA (aDNA) fragmentation: DNA breaks down chemically and physically over time. The oldest recoverable DNA is generally limited to 1 to 2 million years old, making true dinosaur revival impossible. Let alone to make clones out of them.

Reference genome gaps: Using living relatives (such as Asian elephants for mammoths or brown rats for the Christmas Island rat) leaves unrecoverable gaps. Studies show that even with high sequencing depth, 3.4% to 5% of an extinct genome cannot be accurately mapped or filled due to evolutionary divergence.

Loss of adaptive traits: Highly divergent regulatory, immune, and olfactory genes are often missing or malformed in edited genomes, which can compromise the survival of the resurrected animal.

2. Developmental and reproductive bottlenecks

Cloning limits (SCNT): Somatic cell nuclear transfer requires intact, functional cell nuclei—a threshold no ancient, non-frozen specimen has ever met. Even with fresh frozen tissue, success rates remain under 5%.

Surrogate incompatibility: Developing a resurrected embryo requires a closely related living surrogate mother (e.g., an elephant carrying a mammoth or a dunnart carrying a thylacine). Differences in gestation periods, uterine physiology, and maternal-faetal interactions frequently lead to developmental failure or miscarriage.

3. Phenotypic and behavioural mismatch

Learned behaviour is non-genetic: Animals rely on cultural transmission, parental rearing, and social learning for survival skills (migration routes, foraging, and predator avoidance). A proxy species raised by a modern surrogate lacks the lost species' "culture."

Eco-system shifts: Habitats have changed or vanished. If an extinct species' former ecological niche has been filled by other species or altered by human development, reintroduction can trigger competition or act as an invasive disruption. The animal may not survive and thrive in such conditions.

The dinosaurs didn’t live in the same world we live in. Temperatures, climate, microbiomes, flora, and fauna were all completely different. The atmosphere composition was different. Their diets and behaviour were dependent on the species that existed at the time. For example, there is no equivalent today to what the T-Rex diet consisted of—whose hunting patterns were likely very dependent on straight line speed (their ability to pivot and turn would be next to non-existent) and eating absolutely massive animals that you wouldn’t find today.

The germs, bacteria, virus, and everything else the dinosaurs dealt with and were adopted to are completely different. And there’s no telling how dinosaur immune systems would handle modern day viruses and bacteria. Not to mention modern biological study has increasingly revealed just how much we are dependent on various bacterial cells and other foreign species—i.e., you are less than 50% human on a cellular level. This is also likely true of the dinosaurs, who would be without many of the bacteria that were important in their bodily functions.

In a new opinion paper published* in the journal Biology Letters, some scientists argue that bringing extinct species back from the dead isn't quite what it seems.

Their central argument is that genetic engineering cannot truly reverse extinction for several reasons. They illustrate their case with the Dire Wolf Project, in which biotechnology company Colossal Biosciences claimed to have brought this extinct predator back to life.

But this is not what happened. Colossal genetically modified cells from living gray wolves (distant relatives of dire wolves) by making 20 edits across 14 genes. It then used the modified cells to produce cloned animals with some of the characteristics associated with the extinct predators.

According to these scientists, the resulting animals are still genetically engineered gray wolves, not dire wolves brought back from extinction. This is because recreating some of an extinct animal's characteristics doesn't restore its evolutionary history or the genetic diversity that once existed across its population.

"Such organisms may have scientific or conservation value as analogs or ecological proxies, but they are not continuations of extinct lineages," wrote the researchers in their opinion piece.

They also argue that even if scientists could recreate an extinct animal's genetic makeup, they couldn't restore the environment in which it evolved. This includes its relationships with other animals and the conditions that helped shape its evolution.

That doesn't mean the researchers think all de-extinction attempts are the same. "These approaches should not be treated as conceptually equivalent."

They acknowledge that cloning animals from preserved cells or frozen embryos of an extinct species is a different matter. This is because such material could preserve a direct biological link to the original species.

The scientists think that the technologies being developed for de-extinction could serve a more useful purpose. Rather than trying to bring back species that have disappeared, they could help protect those that are still alive by restoring lost genetic diversity and potentially reducing the harmful effects of inbreeding.

Even if scientists somehow succeed in this project using all their capabilities, the operating costs to maintain the dinosaurs would be astronomical. Think of how much this hypothetical park to keep them in the specific surroundings they need would be for each and every genetic extinct specimen that is discovered. Imagine the upkeep costs of the most insanely exotic zoo on the planet. Imagine how much trial and error would go into the refinement of different habitats, as they have to be adopted around newly discovered behaviour. And imagine how enormously expensive this would be from a consumer perspective.

Is it worth the effort? NO!

So forget about meeting the dinosaurs again.

* Andrew Davinack et al., Reconstructing traits, not restoring lineages: the biological limits of de-extinction, Biology Letters (2026). DOI: 10.1098/rsbl.2026.0315

The biological limits of de-extinction

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