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Should cloning be used to revive extinct species?


The issue

In September 1999 a trust was established dedicated to cloning the extinct Tasmanian tiger (also known as a Thylacine).
It is planned to make use of DNA from a number of preserved specimens, including a female tiger pup preserved in alcohol at the Australian Museum.
In October 1999 it was announced that similar efforts might be made to clone a woolly mammoth using DNA extracted from a specimen recently removed from a Siberian ice field.
These proposals have met with a mixed response within the scientific community and the media. There are those who see such moves as a rare opportunity to restore species thought to be irretrievably lost. Others, however, view such efforts as futile, over-reaching and misdirected. The debate continues.


Echo Issue Outline 2000 / 19
Copyright © Echo Education Services
First published in The Echo news digest and newspaper sources index.

Issue outline by J M McInerney

Background
The extinction of the woolly mammoth and the Tasmanian tiger
* During the Pleistocene Epoch, from about 1.5 million to 10,000 years ago, the world grew cold. These conditions seemed to encourage the development of giant mammals, among them the mammoth.
Mammoths were closely related to today's elephants. Mammoths ranged in size from a dwarfed form (two metres high) up to the Imperial mammoth that stood four metres at the shoulder. Mammoth tusks curved downward. They were vegetarians and probably fed primarily on leaves.
Mammoth were hunted by humans and this may have contributed to their disappearance after the end of the ice age.
The dwarf branch of mammoths survived on Wrangel Island in the Arctic Sea north of Siberia until just 4,000 years ago.

* The Thylacine was the largest known carnivorous marsupial. The last record of a Thylacine was from a Tasmanian zoo, where it died in 1936.
It used to be widespread on the mainland about 7,000 years ago and has probably been extinct there for 2,000 years. Competition of dingoes, which were introduced to the Australian mainland at least 8,000 years ago, contributed to the Tylacine's extinction there.
The Thylacine was in Tasmania when Europeans first arrived 200 years ago. It may have already been in decline but this was accelerated by the new arrivals.
Thylacines were seen as a threat to stock and were shot on sight. A bounty was placed on them and thousands of claims for bounty were made which led to the Thylacine's rapid extinction.
The Thylacine's habitat also coincided with the best farming areas. Some were trapped for zoos and these are now a source of records on Thylacine biology in captivity.

A note on cloning and extinct species

It is easiest to begin a discussion of cloning by contrasting it with sexual reproduction.

* In sexual reproduction, two parents are involved. Each contributes a sex cell or gamete. When these gametes join or fuse a new organism begins to develop.
A sexually produced organism will have a genetic make-up which is a combination of that of both of its parents. Physically it will usually display a variety of features, some inherited from each parent.

* As it occurs in nature, cloning is reproduction involving only one parent. It is also referred to as asexual reproduction.
Cloning occurs when a single cell from the parent organism begins to divide and develop in such a way that a new organism is produced. This new organism has exactly the same genetic make-up as its parent and is usually physically identical to its parent.

* Scientifically engineered cloning also involves one parent, to the extent that it is the genetic coding of only one parent which should primarily determine the characteristics of the offspring.
The procedure which may one day be used to clone extinct species such as the Tasmanian tiger and the woolly mammoth would have DNA from a preserved specimen inserted into a sex cell (usually an egg or ovum) taken from another species. This sex cell would have had its nucleus, and thus most of its genetic material, removed.
The resultant artificially created cell would then be 'jolted' in some way into beginning the process of cell division. One method is to use an electric current.
Such a procedure was used in 1996, by the Edinburgh team which produced the first known cloned mammal, a sheep subsequently named Dolly.
In the case of the Tasmanian tiger, it is planned to use the de-nucleied ovum of a Tasmanian devil together with DNA from a preserved Tasmanian tiger. A Tasmanian devil would then act as a surrogate mother for the artificially created Tasmanian tiger zygote.
With the woolly mammoth it is intended to use the egg of an Asian elephant which has had its genetic material removed. The artificially created mammoth zygote would then be implanted into an Asian elephant which would carry it to term and give birth.

It is not expected that this procedure will be easy. The DNA extracted from preserved specimens is unlikely to be complete and may not be viable.

Internet links
The ABC's Science News subsite has a report on attempts to resurrect the Thylacine. The report is titled Genetic Recovery of Australia's Tasmanian tiger? and can be found at http://abcnews.go.com/sections/science/DailyNews/tigerclones990513.html

The Age, on May 13, 1999, published an article titled Unleashing the Thylacine by James Woodford. It gives some early details of the plan to restore the Thylacine. It can be found at http://theage.com.au/daily/990513/news/news4.html

The United States Department of Energy, together with the University of Chicago and Argonne National Laboratories have established an Ask a Scientist Archive where scientific questions and answers are stored.
One of the questions deals with the cloning procedures supposedly used to bring dinosaurs back to life in the film, Jurassic Park.
The question and the answers it received can be found at http://newton.dep.anl.gov/askasci/bio99/bio99083.htm

The Brooks/Cole Biology Resource Centre has an article in its Critical Thinking collection titled Revival of the Tasmanian Tiger. It was written in June, 1999, by Walter Escobar.
The article is a summary of what it is hoped to achieve with the Tasmanian tiger. Of more interest is the set of questions which follow the article. These encourage the reader to consider a number of the possible implications of the project.
The article and accompanying questions can be found at http://www.brookscole.com/biology/member/student/think/crit_think06_99.html

The Roslin Institute On-line has a monogram dealing with Cloning in the conservation of rare breeds. It was written by Harry Griffin and James Woolliams in August, 1998.
It considers the practice as it might be applied to the great panda and supplies answers to four questions which might be asked about such a procedure.
The Roslin Institute was the organisation behind the cloning of Dolly.

The Roslin Institute also has answers to a series of commonly asked questions about cloning.
These can be found at http://www.ri.bbsrc.ac.uk/library/research/cloning/sindyq&a.html
They include a response which indicates that some genetic material is contained outside the nucleus of a cell and therefore any organism produced by splicing DNA from an extinct species with a de-nucleied cell from another species would not produce an identical replica of the extinct creature.

Arguments against cloning extinct species
There are six main arguments offered against cloning extinct species

1. It is very unlikely to be successful.
Russian scientist Alexie Tikhonov has claimed, 'Even assuming an intact mammoth could be found, the chances of isolating a complete DNA molecule is highly improbable ... Even frozen, DNA could not survive thousands of years without deterioration.'
A similar concern has been expressed about attempts to extract DNA from specimens that have been preserved in alcohol.

2. It is a misuse of research and conservation funds which would be better directed elsewhere.
The Tasmanian Conservation Trust manager, Mr Michael Lynch, has said of the proposed attempts to restore the Thylacine, 'When there are so many species of flora and fauna hanging on by their fingernails ... why put a lot of money into a hairy scheme to possibly clone something that has been extinct for 60 years.'
The Thylacine project is expected to cost more than $3 million.

3. It may lead to the mistaken belief that conservation efforts can be postponed because species can
always be revived via cloning.
There is concern that popular support for habitat restoration and preservation could falter and other attempts to limit species exploitation could be reduced. Some conservationists are worried that cloning might be seen as a species safety net, when, in fact, its likelihood of success is small.

4. Any animal successfully produced would be unlikely to survive in the wild and reproduce.
The Age's environment reporter, Claire Miller, has written 'We know little about a mammoth's habitat requirements ... the ecosystems may no longer exist to support the animals in the wild.' Miller has also claimed, 'A cloned creature raised in isolation may well not have appropriate survival skills in any case.' It has also been suggested that successful breeding populations are unlikely to be established via cloning.

5. If any 'resurrected' species could survive in the wild it might upset existing ecosystems.
It has been claimed that if a restored species were to succeed in the wild it would necessarily impact on other species, perhaps to their disadvantage. Any restored species might either prey on or compete with existing species, disturbing current ecosystems.

6. Such resurrection efforts could inadvertently revive viruses that these extinct species carried.
Some scientists have expressed concern that individual specimens of extinct species may have been killed by viruses and that when these animals' DNA was 'resurrected', the viruses, which reproduce within the nuclei of other organisms, would also be released.

Arguments in favour of cloning extinct species
There are six main arguments offered in favour of using cloning to try to restore extinct species.

1. It offers a chance of continued survival for species that would otherwise never again exist.
The New South Wales premier, Mr Bob Carr, has stated, 'We've got the prospect of bringing one of God's creatures back to life.' To those who value the uniqueness of all life forms, this is particularly appealing.

2. It is not mankind further tampering with ecosystems; it is an attempt to restore animals that should not initially have been removed from ecosystems.
One of Australia's leading experts on cloning and in-vitro fertilisation, Professor Alan Trounson,
of Monash University, has said, 'Ecology is upset already. There are rabbits and camels running
around that were not there before.'
Dr Mike Archer, the new director of the Australian Museum, has claimed, 'There's a moral imperative here. It's not God's will that the thylacine went extinct. We did it.'

3. The same technology could be used to help preserve endangered species.
There are already plans to use the similar techniques to help preserve the giant panda and the
white dolphin. The nucleus of a panda cell has been successfully implanted into the egg of a
Japanese white rabbit. It is hoped that the black bear could serve as a surrogate mother for such a
zygote.

4. Though the procedure might be difficult there has been so much progress in cloning that
difficulties are likely to be overcome.
Garvan Institute executive director, Mr John Shine, has claimed of plans to clone a Thylacine,
'You'd be a brave man indeed to say it's not possible ... If 20 years ago you'd said we can isolate a single human gene, scientists would have laughed at you. Today, every diabetic on this planet uses human insulin synthesised from a cloned human insulin gene.'

5. There are not the same ethical reservations about cloning animals as there are about cloning
human beings.
Reproductive biologist, Professor Roger Short, has claimed, 'I don't see anything wrong with it ethically.'
The Age in its editorial of October 25, 1999, made a similar point. '... we do not believe that these ... [reservations about human cloning] can be extended to the animal kingdom.'

6. Cloning extinct species appeals to the human imagination.
New South Wales Premier, Mr Bob Carr, has stated, 'The idea is intoxicating and is remarkable. It will grip the imaginations of young Australians in particular.'

Further implications
It seems highly unlikely that projects such as that to restore the Thylacine will not go ahead. There seems to be significant popular and political support for the idea.
Such projects also represent a major scientific challenge and thus are likely to appeal to the scientific community.
It seems unlikely that, at least in the short term, such attempts to clone extinct species will succeed. In the long term perhaps viable clones will be produced. Whether these will ever result in breeding populations is even more problematic.
What does seem more immediately promising is that cloning will be used to help preserve currently endangered species. Though again, without habit preservation, cloning will do no more than supply specimens for zoos or reserves.

 Sources
The Age
8/9/99 page 6 news item, 'That tiger again! New bid for a resurrection'
9/9/99 page 13 news item, 'Thylacine clone plan condemned'
12/9/99 page 5 (Agenda) comment by A Dyson, 'Forget the Tasmanian Tiger, let's clone Jennifer Paterson'
25/10/99 page 12 editorial, 'Conjuring the woolly mammoth'
9/10/99 page 20 news item by Aisling Irwin, 'Cloning plan to preserve panda'
28/10/99 page 19 comment by Claire Miller, 'A mammoth exercise in vanity' - see media analysis below this list
23/1/00 page 16 comment by Margaret Wertheim, 'You have to admit the thylacine better days'

The Australian
8/9/99 page 8 news item by John Ellicott, 'Science won't let sleeping tigers lie'
23/10/99 page 3 news item by Stephen Brook, 'Mammoth tusk ahead to clone ancient pachyderm'
25/10/99 page 13 news item, 'Intact mammoth a woolly tale'
30/10/99 page 26 comment by R Koval, 'Looking back on an ancient future'
5/11/99 page 13 news item by Tony Allen Mills, 'Melting moment's mammoth appeal'
13/11/99 page 23 analysis by Stephen Brook, 'Mammoth task'
18/2/00 page 10 news item by Lynne O'Donnell, 'Cloning hope for dolphins'
22/2/00 page 3 news item by Stephen Brook, 'Mammoth wool pulled over our eyes'
5/5/00 page 1 news item by Stephen Brook, 'Thylacine clone no longer just a paper tiger'
10/5/00 page 22 letter, 'Preserve the Thylacine's habitat first'

The Herald Sun
9/9/99 page 18 comment by Andrew Bolt, 'Tiger lives - God extinct'
25/10/99 page 19 analysis by Greg Thom, 'Back from the dead'