First introduced as a means to “undo” historic extinctions by reintroducing new versions of extinct species to their original habitats, de-extinction has rapidly emerged as a leading actor on the global conservation stage in the last two decades. In 2003, European scientists were able to clone a Pyrenean ibex, which had gone extinct just years earlier, using DNA extracted from well-preserved tissues. While it died from a lung defect within minutes of being born, the ibex resurrection was a milestone along the path of de-extinction. Today, ambitious projects around the world are leading the charge in the de-extinction of important species ranging, from the passenger pigeon to the Tasmanian tiger to the woolly mammoth. But what does the language of de-extinction really reflect? What is extinction, biologically, and why is de-extinction important? What do its methods entail, and how does it make sense from a conservation perspective?
A Dictionary of De-extinction – Etymology, Definition, and Significance
Life /lʌɪf/ (n.)
Arising from Proto-Indo-European *leyp- for “to stick, glue”, metamorphosized into Proto-Germanic *lībaną for “to remain, stay, be left”, life emerged in its current form in Old English as līf for “life, existence”.
Life is defined as “an organismic state characterized by a capacity for metabolism, growth, reaction to stimuli, and reproduction”, having arisen on Earth 3.7 billion years ago in the form of the earth’s first photosynthetic microscopic organisms. Since, life has evolved into increasingly sophisticated forms of uni- and multicellular beings, organized into three main domains. In order of increasing complexity, these include Archaea, Bacteria (both tiny cells without much internal structure), and Eukarya (multicellular organisms with a nucleus enveloping its genetic code [see “DNA”, “gene”, “genome”]).
Complexity is easy to achieve. The (self-)perpetuation thereof is more tenuous, and a rather phenomenal pillar of the (genetic) evolutionary processes underpinning life and evolution [see “evolution”, “extinction”].
Evolution /ˌiːvəˈluːʃ(ə)n,ˈɛvəluːʃ(ə)n/ (n.)
Emerging in the early 17th century from Latin evolutio(n-) for “unrolling”, from the verb evolvere, evolution was first used in the 1620s to describe “an opening of what was rolled up”.
In biology, evolution represents “the cumulative inherited change in a population of organisms through time leading to the appearance of new forms”. English naturalist Charles Darwin famously established evolutionary theory in the 1800s to explain the emergence of new species as a result of the pressures of natural selection on naturally occurring intergenerational genetic mutations.
“Biology is the science. Evolution is the concept that makes biology unique.” – Jared Diamond (1937-)
Co-evolutionary forces, pressures and processes have guided the trial-and-error emergence of life in its increasingly diverse and complex forms. A product of these, Life as we know it today is a colorful web of symbiotically interacting, creative organisms – slivers of steps in an upward spiral of intelligence and efficiency.
DNA /diːɛnˈeɪ/ (n.)
Deoxyribonucleic acid (DNA) derives from 19th century German Ribonsäure, a tetrahydroxy acid, and Nukleinsäure, or “substance obtained from a cell nucleus”, to form ribonucleic acid. Deoxy is formed from the Latin prefix de for “down, off” combined with the Greek oxys for “sharp, acid”, reflecting the chemical absence of an acidifying oxygen group in DNA.
Rather serendipitously discovered in 1869 by Swiss researcher Friedrich Miescher, the structure having been famously elucidated in the 1950s by American biologist James Watson and English physicist Francis Crick, DNA is formed by two long molecular chains coiled around each other in the shape of a double helix. DNA harbors the genetic instructions for the development, functioning, and reproduction of most known organisms – the recipe book of life.
“The capacity to blunder slightly is the real marvel of DNA. Without this special attribute, we would still be anaerobic bacteria and there would be no music.” – Lewis Thomas, American physician (1913-1993)
DNA is the absolute essence, the substate by which are defined and operate life, evolution by trial-and-error, extinction, and de-extinction. Everything we are known to be, come from, and turn into is an emergent result of the dynamic dance of DNA across billions of years of time and the Earth’s 197,000,000 square miles of space.
Ribonucleic acid (RNA), like DNA, derives from the German Ribose and Nukleinsäure. In contrast to DNA however, RNA is equipped with an acidifying oxygen group.
Discovered step-wise, culminating in the feverish discovery of messenger RNA (mRNA) in 1961, RNA also takes on the form of a long molecular chain. Unlike DNA, it is single-stranded, making it more readily degradable, reflecting its shorter-acting, dynamic cellular functions – being constantly produced, used, and broken down. RNA spans many different types, including mRNA, an intermediary form of DNA destined to be used as a template for the production of proteins (gene end products which carry out their intended function), ribosomal RNA (rRNA), and transfer RNA (tRNA), the latter two being involved in the synthesis of proteins. Fascinatingly, it is thought that DNA evolved from RNA, and that life on Earth was once exclusively in the form of RNA.
Originally from Greek genos for “race, kind, offspring”, gene arose in German as Gen, a supposed ultimate unit of heredity. This turned into genom, as coined by German botanist Hans Winkler in 1920, from gene and for chromosom, the unit of spatial organization of DNA.
A gene is by definition “a unit of heredity which is transferred from a parent to offspring and is held to determine some characteristic of the offspring”. All genes, together, give rise to the genome, or complete set of genetic instructions harbored within and required to build a cell or organism.
“The genome is a book that wrote itself, continually adding, deleting and amending over four billion years.” – Matt Ridley (1958-)
The Human Genome Project, culminating in the complete sequencing (or “reading”) of a human genome in 2003, shed light on the evolutionary history embedded within the fabric of our DNA while opening the floodgates to a new era of genome-centric biomedical therapies. The genome has an intricate three-dimensional organization, the spatial hierarchy of which is tied to the exquisitely finetuned activation of genes which need to act in concert with each other over the course of an organism’s development. However, while all humans roughly share the same patterns of activation of some 20,000 genes, millions of natural variations exist between the genomes of any two humans, most of which are healthy, life-compatible variants that might encode eye color or temperament. This enables a high degree of population diversity, a crucial element to any complex system.
Epigenome /ˌɛpɪˈdʒiːnoʊm/ (n.)
Derived from the Greek epi for “near to, above” and genos, the term epigenetics was introduced in 1942 by British developmental biologist Conrad Waddington.
Epigenetics reflects the many different signals and processes regulating the expression of genes that are not directly encoded within the genome. These signals can range from small chemical tags (such as methyl groups) placed on a sequence of DNA or on the structural scaffolds supporting DNA, to the intricate intracellular spatial conformation of DNA. While largely inherited, the epigenome remains very malleable throughout an organism’s lifetime in response to environmental factors. These range from sleep rhythms to nutrition to exposure to environmental toxins or electromagnetic radiation – reflecting the ways in which individual, cultural and societal experiences permeate our biology and personality.
“Genes are equivalent to blueprints. Epigenetics is the contractor. They change the assembly, the structure.” – Bruce Lipton (1944 –)
The many different forms of epigenetic regulation confer a tremendous number of degrees of freedom to a developing organism, allowing it to respond rapidly to a complex environment. The symbiotic actions of a more static genome and dynamic epigenome underpin the adaptive, resilient architectures of organisms.
Genetic engineering /dʒəˈnɛtɪk ɛndʒɪˈnɪərɪŋ/ (n.)
Engineer first arose in Old French as engigneor, stemming from medieval Latin ingeniare for “contrive, devise”. It emerged in middle English as ingineer to denote a designer and constructor of fortifications and weapons.
Genetic engineering reflects the “group of applied techniques of genetics and biotechnology used to cut up and join together genetic material, especially DNA from one or more species of organism, and to introduce the result into an organism in order to change one or more of its characteristics”.
Research in genetic engineering has truly skyrocketed in the last decades. Discovered in 2012, CRISPR-mediated genetic engineering, which harnesses an ancient bacterial immune system which attacks pathogens by splicing up their genetic material, has emerged as a game-changing gene editing technique which can be leveraged to construct new genetic codes, thus creating and re-creating a newly designed version of an organism – theoretically at scale and ad infinitum. It has been ingeniously harnessed in an astonishing array of contexts, leading to the first engineered genomes giving rise to modified living cells or entire nonhuman and even human organisms.
From Latin conservare, “to maintain”, “to keep intact, preserve, guard”, conservation arose in late middle English in the 14th century.
First used by French physicist Leibnitz in 1692 to describe the principle of the “conservation of energy”, conservation in physics represents the principle by which the total value of a physical quantity or parameter (such as energy or mass) remains constant in a system which is not subject to any external influence.
“Here is your country. Cherish these natural wonders, cherish the natural resources, cherish the history and romance as a sacred heritage” – Theodore Roosevelt (1858 – 1919)
As applied to the Earth’s environment, conservation is the practice of protecting the natural world in order to 1) conserve it as it stands, preventing the wasteful use of resources, but also 2) repair damage and 3) reverse trends. In this context, de-extinction forms a core pillar of conservation initiatives – directly contributing to the reparation of damage and reversal of current extinction trends.
Keystone species /ˈkiːstəʊn ˈspiːʃiːz/ (n.)
Species was coined as a Middle English word in the 1550s, originating from the Latin species for “appearance, outward form”. Derived from Old English cæg for “key”, a keystone arose in the English language in the 1630s to designate the “stone in the middle of an arch which holds up the others”.
A keystone species, as introduced by American zoologist Robert Paine in the 1960s, is one which holds up the others within the arch, or web, of an ecosystem. Paine had originally coined the term to explain the relationship between a species of starfish and mussel: the innocuous removal of starfish from a local Pacific tide pool community caused a dramatic drop in many different species of algae, anemone, and sponges, directly resulting from a rampant population of mussels normally kept in check by the predatory starfish. Keystone species such as starfish have a crucial, disproportionate impact on an entire ecosystem relative to their population.
Current conservation-oriented rewilding projects, which emphasize landscape-scale restoration, usually include the reintroduction of keystone species. Such species can be predators (as in the case of starfish in Pacific tidal pools or wolves in Yellowstone), herbivores (contributing to the regulation of an ecosystem by consuming plants), or any other types of species which, alone or in symbiosis, play a critical role in the architecture and regulation of an ecosystem.
De-extinction /ˌdiːɪkˈstɪŋ(k)ʃn/ (n.)
De-extinct /.di;ɪkˈstɪŋkt/ (v.)
Formed from the prefix de from Latin for “down, down from, from, off” and the Latin exstinguere for “quench”, de-extinction arose as a term in the 20th century in response to a series of breakthroughs in resurrection biology.
De-extinction reflects the “process of resurrecting species that have died out, or gone extinct”. Various such methods have been developed over the last few centuries, including back-breeding (based on the principles of selective breeding to increase the presence of specific traits within a population), cloning (the identical replication of an organism’s genetic material), and genome editing (through genetic engineering).
“Biological diversity is messy. It walks, it crawls, it swims, it swoops, it buzzes. But extinction is silent, and it has no voice other than our own.” – Paul Hawken (1946-)
The ability to de-extinct a species is an infinitely powerful method to bring back extirpated species as a conservation effort. The global conversation on de-extinction methods, priorities, and ethics has been in full force in the last decade as a result. The International Union for the Conservation of Nature (IUCN) developed a set of Guiding Principles on Creating Proxies of Extinct Species for Conservation Benefit in 2016, while conservation biologists from the University of California in Santa Barbara (UCSB) published a set of priorities for selecting species to de-extinct. These would need to 1) have gone extinct recently, 2) be truly ecologically unique, and 3) be able to be restored to abundance levels. Colossal to this end aims to de-extinct precisely selected individual genes (upwards of 50 from the woolly mammoth) conducive to the genesis of a contemporary Arctic ecosystem-compatible proboscidean – fertile soil from both a population diversity and ecosystem conservation standpoint.
Life, DNA, Genetic Engineering, and De-extinction: Key Ingredients for a Sustainable Tomorrow
According to many conservationists, “humans and their technology are not alien intrusions on the world, but rather an integral part of it […] humans should strive to be gardeners in nature rather than preservers of it”. Capitalizing on Nature’s genetic genius, de-extinction – as a conservation strategy to bring back keystone species through genetic engineering – harnesses our growing understanding of DNA, RNA, and genetic engineering methods to lay the foundation for the harmonious and sustainable co-existence of Life in all its most diverse forms – past, present, and future.