The following article was published in “RESEARCH INSIGHTS OF LIFE SCIENCE STUDENTS (Volume - 1)” by JPS Scientific Publications in 2020.
EXTINCTION AND DE-EXTINCTION OF ANIMALS
Meehir Deepak Pawar
B.Sc. Zoology, Department of Zoology, Bhavan’s
College, Andheri (W), Mumbai, India
E-mail: meehirpawar@gmail.com
The word ‘Extinction’ generally
refers to the process in which species of animal or plant is terminated from
environment. The species is then said to be extinct. Extinction generally takes
place due to Natural or Human activities. The Natural Extinction takes place because
of natural phenomenon like disasters, natural selection, genetic variations, inbreeding,
predation, diseases, climate change, etc. Generally, in natural extinction the main
cause is that organism is not capable of adapting according to the changes in
nature. But results in extinction due to human activities are much more drastic
than natural extinction. Human activities like deforestation, introduction of
non-native species, hunting, poaching, transmission of infection through livestock
or crops, pollution after industrial revolution, overfishing, population boom,
invasion, overharvesting, ocean devastation, etc. has led to extinction of many
species. Five mass extinction events were caused by geologic and climatic
events. Human-caused mass extinction event in Holocene epoch called as Holocene
extinction or Anthropogenic Extinction. It is said that it began when the early
human species started defaunation (hunting) and deforestation. Earth is
undergoing early stages of Holocene Extinction and nearly 20% of all living
population will be extinct in 30 yr i.e., by 2028 if conservative measures are
not taken, this was the outcome of survey in 1998 by New York's American Museum
of Natural History and the survey was done by 400 biologists. As per noted in
IUCN Red List Of Threatened Species, 36% of 47,677 species evaluated are
threatened with extinction which represent 21% of mammals, 30% of amphibians,
12% of birds, 37% of freshwater fishes, 70% of plants and 35% of invertebrates.
Revival of extinct species or creation of organism similar to an extinct species is called as 'De-Extinction'. The outcomes and methods of de-extinction are incredible. De-extinction is also of two types; Natural and Artificial. Natural de-extinction is caused by Iterative Evolution. Iterative evolution means repetitive evolution of same structure of organism in different timeline from same ancestral lineage. Most common example of Iterative evolution is of White Throated Rail (Dryolimnas cuvieri) endemic to Madagascar thought to be extinct when Island of Aldabra disappeared under sea around 1,36,000 yr ago but was recently successful to re-colonize the Aldabra island again and became flightless like their ancestors after migrating from Madagascar. After incredible development in the biotechnology field, it is possible to revive extinct organisms depending on the condition of their fossils or preserved specimens. The artificial De-extinction is done by cloning, in vitro, reconstruction of genome, genome editing, CRISPR, back breeding, etc. The process of cloning is generally said to be most potential method for restoration of extinct species. In this process, isolation of nucleus from the preserved cell of extinct species and transferring it into enucleated egg of closely relative species and then the insertion of that egg into closely related species of the extinct animal is done. This process is only done if the preserved cell is available. In case of genome editing, the germ cell can directly be edited so that the extinct parents will produce the offspring of extinct species. This technique is used by the scientists for the species whose preserved specimens are highly degraded. Genome editing or Genome reconstruction is highly advancing nowadays so this can be a better option for De-extinction. Back breeding is a kind of selective breeding which is used to gain the ancestral traits of the species though this is not seen much effectively in many species. Cloning of Woolly Mammoth (Mammathus primigenius) is being done by George Church and his team at Harvard. The Cloning of Pyrenean ibex (Capra pyrenaica pyrenaica) Iberian wild goat endemic to Pyrenees was experimented by Two Spanish and a French team of Scientists. Revival of Aurochs (Bos primigenius primigenius) are being attempted by matching DNA sequence of primitive cattle to that of ancient DNA sample from aurochs by Dutch-based Tauros Programme. Many attempts of de-extinction of Tasmanian Tiger (Thylacine cynocephalus) recently extinct Carnivorous marsupial endemic to Tasmania have been done and are in progress. Similarly, de-extinction of Passenger Pigeon (Ectopistes migratorius), Quagga (Equus quagga quagga), Dodo (Raphus cucullatus), Heath Hen (Tympanuchus cupido cupido), and much more experiment are going in various laboratories across the globe. Why is there any need to revive any extinct species? The answer is to conserve environment and advancement in research. Introducing the extinct species back to its environment can help the nature to revive. The ecosystem which was destroyed by human activities will be revived again. The current conservation strategies will be helped by the revived species. George Church, a Harvard geneticist, working on Cloning of Woolly Mammoth said, “A revived Woolly Mammoth can help in reversing the ill effects of global warming”. He and his team predicted that Mammoths can eat dead grass so that sunlight can reach spring grass, their weight can help to break down the thick and insulating layer of ice so that cold air can reach the soil. Thus, there will be positive effects on environment after revival of woolly Mammoth. Advantages will be majorly in each research field related to life sciences like understanding behaviour of a prehistoric or extinct animal, ethology, anatomy, physiology, morphology, developmental biology, processes occurring inside the organism, prehistoric diseases will be the major topics for research purposes. Strategies to conserve currently endangered species will become more efficient. Thus, De-Extinction of many extinct species will have positive effect in every research field of Life science and on Environment.
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