De extinction definition

According to IUCN's Guiding Principles on Creating Proxies of Extinct, 2016, "the term de extinction is misleading in its implication that extinct species, species which no viable members remain,can be resurrected in their genetic, behavioural and physiological entity. It is therefore here used in a limited sense to apply to any attempt to create some proxy of an extinct species or subspecies."

Colossol Bioscienes Inc, definition of de extinction states that, "The process of generating an organism that both resembles and is genetically similar to an extinct species by resurrecting its lost lineage of core genes, engineering natural resistances and enhancing adaptability that will allow it to thrive in today's environment of climate change, dwindling resources, disease and human interference." - The definition does not say what are core genes or how enhancing adaptability would still ensure replica of that target de extinct species.

Technological mechanisms

Cloning
Back breeding or selective breeding
Genetic engineering

Aenocyon Dirus, alias Dire Wolf

The Dire wolf also known as, "Aenocyon Dirus", hunted in packs, and fed on horses, ground sloths, and bison. It supersized its contemporaries.
Adapted to diverse habitats like boreal grasslands, coastal woodlands, and tropical wetlands.
When earth entered the holocene epoch, there increased a competition for food between packs, and also possibly between humans and dire wolves.
They went extinct between 13,000 and 10,000 years ago.

Resurrection of dire wolf

Resurrected in 2024, and announced on April 7, 2025 by the US based Colossal Biosciences Inc., "World's first de extinction."

The company introduced the 6 month old male pups Remus and Romulus, and also confirmed the birth of a 2 month old female, Khalessi. The names are taken from George R R Martin's book "A song of ice and fire", who also happens to be an investor in the Colossal.

CRISPR Cas 9

The pups primarily possess the gray wolf DNA, modified to give the appearance of the dire wolf, as both share 99.5% of their DNA. This was done through gene editing CRISPR (clustered interspaced short palindromic repeats) technology. The enzyme used is Cas 9. The surrogate maternal hosts who birthed the pups were dogs.

It is not a dire wolf, but a gray wolf modified to be more like a dire wolf.

Dolly, 1996

The first successful and the most known mammal cloning bid was of Dolly, the sheep in Scotland in 1996.

Wolly mammoth

Wild new breeds of hybrids such as wolly mammoth, which died out 4,000 years ago, which the company aims to revive using Asian elephants, mammoth's closest living relative that shares 98% of its genetic code.

Hybrid mammoths can help reduce warming with their grazing , which would scrape away layers of snow, allowing cold air to reach the soil and preventing snow from melting quickly. The benefits can happen if you have self sustaining populations. How many thousands of mammoths are you going to need trampling over siberia to achieve this?

Thylacine, from Australia

Next is Thylacine or Tasmanian Tiger or Tasmanian wolf, a marsupial from Australia, went extinct due to excessive hunting, habitat destruction and disease. Bringing back this, would control the rampant, invasive rabbit populations in Australia, that threatens the native plant and animal species. There were killed by humans, for the fear that they might kill sheep

Dodo project

Another resurrection project is for dodo, the most known extinct birds globally, native to Mauritius. Died due to deforestation, hunting and destruction of nests by animals brought by Dutch. Nicobar pigeon, is one of the dodo's closest living relative, which can be used in the resurrection process.
Tatayah, belongs to the Indian ocean island of Mauritius, where Dutch settlement in 1600s wiped out dodo

Traditional selective breeding

Traditional selective breeding, involves choosing parents that possess certain physical or morphological traits and breeding them through several generations, till the offspring appears physically similar to lost species.

The Quagga Project, 1987 - South Africa

South African scientists in 1987 launched a de extinction efforts called The Quagga project and bred living southern plains zebra populations, that showed some quagga characteristics. The fourth generation of the offspring possessed the reducing stripping of the hind body and legs but lacked the same colouration. These were called Rau Quaggas, released into the wild.

Tauros, 2023 - Netherlands

In Netherlands, a selectively bred livestock to reverse certain genes and bring back extinct Aurochs, the ancestors of all living cattle. It is called Tauros, released into the wild since 2023.
You cannot reproduce the lost species, in the best case, you can build look alikes with some of the genes, hence the name "Tauros" not "Aurochs."
The programme aims to rewild the large depopulated areas, so the herds together with other large grazing animals restore the park like landscapes, once were very common in Eurasia.

Plants

The extinct plants can be truly revived if their seeds are viable for germination. But what if they become invasive?

Advantages

This can be a way to conserve critically endangered species.
Addressing the lack of diversity through cloning
Played an essential role in stabilising the ecosystem, like Thylacine in Australia
Reverse the biodiversity crisis
Restore the ecosystem functions
- when an animal goes extinct, its functions in the ecosystem are lost, like dispersal, predation, control of certain plants, pollination

Disadvantages

Cloning suffers from low efficiency, with a success rate of only 5 to 10%.
Risk of invasiveness
Disease transmission
unforeseen species interactions
The process is unnatural with unknown consequences and impacts, if the plan is to rewild the de extinct species.

Ethical concerns

What is the point of bringing them back
- Is it for human entertainment or
- does it serve some environmental benefits
Could the resources and money spent on de extinction decrease the same meant for conservation programmes for the extant species
De extinction could give the impression that extinction is reversible thereby undermining the seriousness of human actions that lead to extinction of species.
Deep de extinction does not address any pressing ecological or social problems, and it does not make up for the past harms or wrongs. Taking on significant costs or risks or funneling scarce resource to pursue it is not justified.

Questions to be answered?

It is still early to say if the pups behave like dire wolves
Where they will be released
Quite difficult to find space to even conserve extant species
Question of climate change and adaptability of the newly created animal
- Wolly mammoths lived in ice age climate, when the average temperatures were up to 12 degree celsius colder than today.
Reasons for the animal to become extinct are still relevant today, then how do they sustain now, if not then?
We should prioritise protecting the species that currently exists and are at the risk of death rather than bringing back those that are already dead.

Health of the animal created

problems pertain to the animal created and surrogate used in its birth.
Dolly, was plagues with arthritis, lung disease and died at 6 years, whereas a normal sheep lives up to 12 years.
US company, in 2000, cloned a Bucardo or Pyrenean ibex, from the last individual, but the animal died within minutes of birth.

Critical issues by Browning, 2018

Problems in birth, with target animal being larger or differently shaped than the surrogate, case with elephants carrying mammoth babies.
Surrogate could reject the unusual offspring
Animals created would grow in absence of elders of their species, unlikely to have the required behavioural repertoire and social vocabulary to match their mammoth companions.

Emergence of private ecosystem

US based company, ViaGen pets and Equine clones deceased pet dogs or cats at a cost of $50,000.

Indian example

The Indian council for Agricultural Research National Dairy Research Institute, Karnal, has cloned cows and buffaloes , including the indigenous Gir cow.

56 cloned

Globally 56 species and sub species have been cloned since 1956 as per a 2025 review paper in Animals magazine.

Pics

Resurrection lined up

Lessons in conservation

Protected areas, most common method for conservation

IUCN red list category

Conservation actions and results