Course:CONS200/2021/De-Extinction of the Woolly Mammoth

A Brief History

The woolly mammoth, Mammuthus primigenius , was a large mammal related to modern day elephants, existing during the Pleistocene and going extinct during the Holocene era an estimated 4000 years ago. With advances in genetic technology, it has now been made possible to clone, modify and recreate creatures that have long since been extinct and scientists aim to do exactly this with the woolly mammoth. Though actual DNA fragments recovered from fossils are far too damaged to use in resurrecting this ancient mammal, scientists aim to genetically modify its closest living relative, the Asian elephant, until it is virtually indistinguishable. While some argue that recreating the mammoth will benefit the tundra ecosystem, the plan to bring back a long extinct species has caught significant criticism and scrutiny from scientists and the public alike.

Extinction of the Woolly Mammoth

Image of a Woolly Mammoth

The woolly mammoth is believed to have gone extinct during the Holocene era, overlapping briefly with human civilization. Their disappearance is thought to be mainly attributed to the quick climate change that occurred after the Ice Age, altering the ecosystem and damaging vital vegetation needed to sustain larger populations of the mammoths. Co-existing with humans also came with unprecedented predation, and some scientists argue that hunting may also be a contributing factor to their extinction. It is widely accepted, however, that the main reason behind their extinction was not driven by man, and was an inevitable by product of the changing climate.

What is De-Extinction?

Overview

De-extinction is the humanly-performed process of recreating an organism that is a member of, or is very closely related to a previously extinct species. This scientific phenomenon is a result of recent advances in bioengineering and can be done in numerous ways. However, most if not all of these methods have received mixed feedback from the scientific community and have varying degrees of success.

Various Methods

With advancements in science technology have come various methods of enacting de-extinction, each with their own challenges and levels of contention. Below are the various forms currently being explored by science: The woolly mammoth project uses the genome editing method, and will be the topic of focus when referencing its de-extinction.

Back-Breeding

Back breeding consists of selectively breeding to enhance specifically targeted traits. The aim of back-breeding is to bring back the qualities lost in extinction and produce a species as a similar to the extinct one. This is done consistently throughout a population until a previously extinct trait is restored in a population. As one of the oldest methods of de-extinction (beginning in the 1920s with the cattle species auroch) this method has shown potential for success, however the main drawback is that it requires the targeted trait to exist with a currently living population of that species.

Cloning

This technique requires creating an exact genetic replica of an organism using a procedure called somatic cell nuclear transfer (SCNT), whereby somatic cells are injected into a cell lacking a nucleus and cell reprogramming can take place. While this method has also been successfully implemented with various species, and unlike back-breeding can provide an exact genetic replica of the intended species, it can pose challenges when attempting de-extinction. This is because cloning requires a living and intact cell from the extinct species which are incredibly rare to come across. While frozen cells have been successfully clones, often damage to the DNA has occurred and can not produce viable offspring.

Genome Editing

This de-extinction effort combines extraction of ancient DNA and re-sequencing a genome to resurrect an extinct species. Though intact cells required for cloning are very challenging to acquire, genome editing can use partially damaged DNA from an extinct animal, so long as the sequencing can be read. Once the original sequence has been read, genetic engineering can be performed to alter a fertilized cell of the species’ closest living relative in vitro. This method of de-extinction, while it tackles many of the challenges presented in the aforementioned techniques, has some issues of its own. Though DNA samples do not need to be in perfect condition, colder temperatures facilitate a better preservation than do warmer temperatures. This means that many species previously existing in hotter and wetter climates are much less likely to have readable DNA to be used for de-extinction. There also must be a closely living relative with DNA similar enough to modified- something that does not always exist for extinct species.

Similar Cases of De-Extinction

A similar definition of de-extinction was set out by the IUCN stating “de-extinction is the ecological replacement of an extinct species by means of purposefully adapting a living organism to serve the ecological function of the extinct species by altering phenotypes through means of various breeding techniques, including artificial selection, back-breeding and precise hybridization facilitated by genome editing. The goal of de-extinction is to restore vital ecological functions that sustain dynamic processes producing resilient ecosystems and increasing biodiversity and bio abundance. This form of de-extinction has been practiced throughout time, forming replacement populations as a method of modern de-extinction. A successful example of de-extinction via breeding was the restoration of the North American eastern peregrine falcon. Using survived populations from the west and north to create hybridized individuals, these interbred subspecies were released into the environment where then the most successful genotypes/phenotypes were selected. Because of this intentional release of hybridized individuals, peregrine falcons have recolonized urban, suburban and wilderness areas throughout the eastern United States. This is an example of modern-day de-extinction using breeding to restore populations. However, for the case of the Woolly Mammoth, extensive biotechnology would be needed for de-extinction. Only precise hybridization via genome editing would be viable for many de-extinction candidates, as it uses the genome sequence of the extinct species and a living species as template whose genome can be edited to express the allele of the extinct species. Fossils dating as far back as 700,000 years ago have had their genomes sequenced making many species from the Pleistocene and Holocene potential candidates for this hybridization. George Church’s team at Harvard has edited 44 loci of the Asian elephant genome, to which the elephant is theoretically ready to act as a proxy for the woolly mammoth.  

Conflicting Opinions on De-Extinction

Members of the scientific community and the public alike are largely divided over re-introducing the extinct mammoth to the tundra. The project leader, geneticist George Church, argues that these newly created species of “woolly mammoth”, or at least something that looks and acts exactly like them, will help in reversing climate change and restoring arctic conditions. This is because the woolly mammoth would regularly strip the earth of layers of snow, allowing the cold temperatures to continuously reach the soil and sustain a permafrost. Without the mammoth’s to strip this layer, the snow packs tightly against the earth, allowing it to heat up and melt this permafrost; the result was a release in greenhouse gases. Scientists also believe that this type of genome engineering can help pave the way to a world protected from loss of biodiversity and aid in alternative conservation efforts as well.  

On the other side of the spectrum, many are more than skeptical of the claims that re-creating the mammoth could have any benefit to our climate or ecosystems, simply citing the lack of evidence to their hypothesis. In fact, many scientists believe that needlessly introducing a new species to the tundra, or any habitat, could actually have detrimental effects on the planet.

Controversy in Conservation

Much controversy arises from the idea that resources are being allocated towards bringing back ancient animals, but letting our existing ones disappear. It is estimated that one fifth of vertebrae species are threatened with extinction . A key point made for this argument, is that these threatened species are not yet extinct, and although this may be a dramatic loss in species, it does not yet qualify as a mass extinction in the paleontological sense (comparing it to the previous big 5 mass extinctions) . However, many of the existing threatened species are due to anthropogenic activity, which must be reversed if we want to slow this decline in biodiversity. At a phylogenetic level, the potential benefits of saving current threatened species far outweighs the potential benefits of resurrecting a few extinct species.

Asian elephants are being considered a proxy to de-extinct woolly mammoths

Doubts

There are many questions being asked in terms of whether or not de-extinction actually has potential to restore evolutionary values of lost biodiversity. It was recently argued that ‘deep de-extinction’ will not restore a species natural-history properties, wilderness or independence from humans. This is due largely in part to the idea that de-extinction will likely only result in reconstructed genetic makeup of an organism who most similarly represents the extinct species (in this case – the Asian elephant) . There is also debate surrounding the idea of de-extinction in evolutionary terms. Evolution occurs through the change in allele frequencies across a long period of time and does not include instant heritable changes in species traits or functions of the individuals themselves . So the argument that de-extinction may have the potential to restore some historical patterns to further influence future evolution is short sighted when considering that it is impossible to restore past dynamics of co-evolution between the target organism and their environment. If we were to bring back the Wooly Mammoth, there is a chance that there will be a low eco-evolutionary experience for the species since the ecological functions the Mammoth had on its environment would have been fulfilled by evolutionary changes that occurred since its extinction. This in itself, is the main drawback when considering the evolutionary value of de-extinction. According to a recent journal, de-extinction is only justifiable if it is used to reverse anthropogenic action. This would constitute a short-term evolutionary scale of a few tens or hundreds of generations since the extinction of a particular species. In this way, de-extinctions would be justifiable in both an evolutionary and ethical stance in that it would preserve DNA and resolve extinction events caused by negative human impact .

Benefits

Similar landscape that woolly mammoths roamed

The main goal of ongoing de-extinction projects is to create functional equivalents of species that once existed. With the hopes of using an Asian elephant as proxy for the Woolly Mammoth, these modified elephants would be able to survive through cold Siberian winters and replace mammoths in that landscape. Having these mammals graze, recycle and disperse nutrients through the land would help to maintain a diverse and healthy ecosystem. De-extinction of the Woolly Mammoth is also putting forth an effort towards combatting climate change. In the steppe grassland ecosystem, millions of metric tons of carbon are stored in pools and the Mammoths would help keep these carbon pools and greenhouse gases ice bound for longer. Ultimately, the goal of cloning mammoths is to see how they can shape and maintain the environments they were traditionally found in, however their benefit to science may be more diverse as the technologies employed to de-extinct them may be farther reaching. Researchers also believe that resurrecting this extinct species could provide a fundamental shift in the narrative towards conservation efforts; changing often negative rhetoric to hopeful attitudes in the potential success rates. This increase in interest towards the field of conservation is expected to expand funding sources for further projects that could prove very beneficial to preservation efforts.