Back from extinction

Imagine if you could bring a species back from extinction – what would you choose and why would you choose it? There are so many factors to take into consideration it all becomes a bit bewildering – do you choose something on the basis of how well it would reintegrate with existing ecosystems, how useful it might be, how much novel information we could learn from it, how plausible it would be to actually carry out the resurrection process, or simply how awesome it would be to see something that hasn’t walked the Earth for millions of years?

I recently asked four palaeontologists what species they would choose to resurrect and their responses were presented at a Café Scientifique balloon debate at the Horniman Museum, as part of the International Year of Biodiversity activities in conjunction with the Royal Society (who are celebrating their 350th anniversary!). The result was a very enjoyable evening for all involved and an insight into some of the considerations that should be taken into account when contemplating resurrecting extinct species.

The contributors were Anjali Goswami who is a lecturer in palaeobiology at UCL, Mark Carnall who is the curator of the Grant Museum of Zoology and Comparative Anatomy, David Waterhouse who is a curator at Norwich Castle Museum and Tim Ewin who is a curator at the NHM. Each of them came from a very different angle and each gave a very informative and entertaining ten minute presentation to persuade the audience that their species should be brought back from extinction. Before I introduce the species chosen and summarise the presentations, I should probably provide a bit of context, as I did on the evening in my role as host/chair/referee.

Biodiversity is a big idea – it encompasses the variety of all aspects of all organisms on the planet (and perhaps beyond, should extraterrestrial life be found). Biodiversity exists as a concept in the future and past as well as in the present. Most of the diversity of life that ever lived on this watery ball we call Earth has disappeared in the 3.6 billion or so years since the first simple self-replicating chemical system kick-started our very long and bushy lineage.

However it is the last 542 million years (known as the Phanerozoic or Eon of visible life) that have really given us the bulk of biodiversity and in that time we know from the fossil record that biodiversity has been increasing at the generic level, with mass extinctions potentially providing a spur for diversification at the cost of short term depletion in diversity. Of course, this is just at the generic level and it seems reasonable to suggest that mass extinctions have also led to longer term depletion in variety at a more fundamental level – the basic shape of what’s out there has become more conservative as biodiversity has passed through bottle-necks like the massive Permo-Triassic extinction.

Resurrecting some of this past biodiversity has long been in people’s minds in one way or another, from ancient myths about monsters like dragons, unicorns, Cyclopes’ and such, to more recent fictitious accounts based on more systematically described prehistoric beasties: Sir Arthur Conan Doyle’s The Lost World, Jules Verne’s A Journey to the Centre of the Earth and Merian C. Cooper‘s King Kong relied on refuge populations of prehistoric beasts that survived for tens of thousands of millennia in unchanging isolation, without leaving any evidence of their existence for all that time. Obviously this scenario is unlikely given our modern understanding of continental drift and fluctuations in global climate, but a small number of such refuge species do exist out there. These are called Lazarus species, which appear to have gone extinct, but are then found after a substantial period without any fossil finds or sightings in between. Real life examples include the Coelacanth (80 million year gap in the fossil record), the Wollemi Pine (2 million year gap) and the Laotian Rock Rat (11 million year gap). On top of these current living fossils the geological record also contains a variety of Lazarus species (as well as Elvis species and even Zombie species) that suggest there is a crumb of validity for the prehistoric survivor hypothesis (although only a crumb – see Darren Naish’s excellent Tetrapod Zoology blog for discussion, or even better, come to his talk about this very topic on the evening of the 25^th May 2010 at the Horniman).

Nowadays our cultural reference on resurrecting species comes directly from Michael Crichton’s Jurassic Park, where dinosaur DNA is extracted from mosquitoes preserved in amber and recombined with frog DNA to enable production of a superfast T. rex and a gang of giant, ubersmart Velociraptor. This approach to rebuilding extinct species is unlikely to work for dinosaurs, since although DNA can be recovered from 135 million year old insects fossilised in amber, that DNA is incredibly fragmented and is missing too much information to provide the full blueprint for a working gene, never mind an entire organism. That said, more recently extinct organisms may stand a better chance of being resurrected using a similar method. There is excellent DNA preservation from mammoths frozen in ice and 80% of the mammoth genome has already been mapped (pdf). Moreover, the reason there isn’t a complete map of the mammoth genome is due to financial, rather than practical, limitations.

A step in the direction of cloning extinct species has been taken by resurrecting a working gene from the extinct marsupial carnivore Thylacine (AKA the Tasmanian wolf or tiger) in a mouse. Of course it takes more than DNA and working genes to give rise to a living organism; a viable egg must be produced and the developing embryo sustained until it becomes independent. However, cloning technology has made incredible advances over the past decade and if it continues to advance there is a good chance that methods will be developed that will make the cloning of an extinct species a genuine possibility in the not-too-distant future. In fact, for extinct species with close living relatives (like the recently extinct Pyrenean ibex) that future is tantalisingly close.

A different method of resurrecting extinct species may come from an evolutionary development (EvoDevo) perspective. By identifying the genome of an extinct organism it may be possible to selectively breed back to that genotype from living descendents. This neatly solves the problem of providing the maternal machinery required for rearing resurrected genotypes successfully, since the machinery is effectively being retrofitted with each generation. Attempts are being made to use this method for back breeding aurochs right now.

This goes beyond previous attempts to back breed to an ancestral state, since rather than trying to create something that merely looked like it was an ancestral species (something the Nazi’s attempted with the auroch), we are now able to aim for the same genome. If it walks like and auroch and moos like an auroch it still might not be an auroch, but if it has the exact same DNA as an auroch as well, then it really is an auroch.

This process could potentially be taken a step further. For example, if you wanted to create a theropod dinosaur you could use a chicken (or tinamous, or ostrich – any bird will do) as a start point, then start identifying and switching off those parts of the bird’s genome that make it a bird rather than a theropod dinosaur (shut off beak development, switch on tooth development, turn on tail development, etc.). This process would not really be resurrecting an extinct species; it would be creating a new species with the bodyplan of an extinct group of organisms.

Bearing all of this in mind, let’s move on to finding out about which species have been chosen by our panel of experts and the justification provided for their resurrection:

Anjali Goswami: Chaeropus ecaudatus (pig-footed bandicoot)

• The only hoofed marsupial ever
• Lived all over South and Central Australia until its extinction in the early 1900’s
• Could have been the seed of a major marsupial radiation

It would be good to bring back this species because: We’re responsible for its extinction. Marsupials are constrained in their forelimb morphology because they need their forelimbs to function like hands early in their development, as they have to crawl into their mother’s pouch:

However, the pig-footed bandicoot was unique amongst marsupials because it had hooves on its forelimbs as an adult. We have no way of knowing how the development of these hooves occurred because we have no access to baby pig-footed bandicoots showing the development. The fact that the pig-footed bandicoot had managed to develop hooves shows that the standard marsupial developmental constraint must have been broken by this fascinating animal. It is precisely this kind of barrier-breaking to establish new morphologies that has led to major diversification in other animal groups; the incisors of rodents, the wings of bats, and the hooves of ungulates. The pig-footed bandicoot may have had the key innovation that would have started the next major marsupial radiation – contributing hugely to future biodiversity.

Reasons to be careful: Not many! The issue is really more about keeping the resurrected species alive – which requires control of dog, cat and rabbit populations, change in land use and a return to traditional Aboriginal land management practices in designated areas of the Australian interior. These steps would be beneficial for other indigenous Australian species as well.

Mark Carnall: Doomsday virus, or Archaeopteryx (first bird)

• Humans are the greatest threat to biodiversity
• A Doomsday virus from deep time could wipe out the human threat…
• …or a figurehead species like Archaeopteryx could help educate people about the importance of biodiversity and thereby reduce the threat posed by humans

It would be good to bring back this species because: We already have lists of thousands of recently extinct, endangered or data deficient species, so adding another one with our palaeo species is undesirable. Rates of extinction are thousands of times higher than we see in the past –we are responsible for a global mass extinction event right now. A virus from deep time (that our immune systems have not been exposed to before) could wipe out the whole human population, giving the Earth a shot at regaining its ‘biodiversity equilibrium’.

Since this option is unlikely to work without other disastrous consequences (or be very popular with voters) I have a fall-back plan to help educate the world and get people interested in biodiversity. Recent headlines have shown that there is still a great deal of ignorance around environmental conservation and extinction from the highest levels of government through to the latest generation of school leavers. In Europe we like to think that astounding deliberate misinterpretation or misguided hijacking of biological principles to support racism, sexism or homophobia is something that occurs in specific parts of America. Controversy earlier in 2010 surrounding the Pope’s comments on the Equality Bill as well as suggested compromises to sex education for faith schools shows that the fight to educate people about evolution is still very much on.  Furthermore, the ‘accidental’ extinction of the Yangtze river dolphin in  2007,  the largest animal to go extinct in 50 years, highlights that even though we are perhaps more environmentally aware than we have ever been as a species, it is still not enough. We need a figurehead species for the whole of palaeobiology, ecology and environmental biology.  For this role I choose the first ever bird – Archaeopteryx lithographica.

Archaeopteryx has been the unofficial standard bearer for evolution almost since the publication of Darwin’s Origin of Species.  Archaeopteryx is an animal that has features of both birds and reptiles and as such cannot be so easily put into the ‘reptile’ or ‘bird’ boxes.  Ever since its discovery scientists have used, or misused, Archaeopteryx to further their own views about the nature of evolution. In 1861 at a Royal Society presentation Richard Owen tried to quietly write Archaeopteryx off as simply another bird but he was trumped by an anonymous writer to a national newspaper describing the key reptilian features and the resplendent fossilised feathers. Even the normally vociferous Thomas Henry Huxley was silenced by Archaeopteryx as it did not fit his views on bird evolution. Charles Darwin himself wrote various correspondences to his friends enquiring about the enigmatic fossil and included a short paragraph on the beast in the sixth edition of On the Origin of Species.  Since then, Archaeopteryx was unsuccessfully discredited as a forgery, became the frontline in the battle over bird origins between ornithologists and palaeontologists and was briefly superseded by at least two species claiming to be the oldest bird both of which were later discredited.

Archaeopteryx has seen off numerous historical threats to the intellectual study of evolution and man’s place in the Universe and so makes for an ideal candidate to help enthuse people about understanding and ultimately saving biodiversity.  Secondarily, Archaeopteryx could provide lots of interesting information about the evolution of flight, the dino/bird transition and feather evolution

Reasons to be careful: A Doomsday virus might kill off more than humans – other primate species would be the most likely casualties. Archaeopteryx is unlikely to cause any particular problems except by challenging the beliefs of religious extremists, which may result in violence, since people without a coherent argument or evidence in support of their opinion tend to resort to force and intimidation as their only methods of persuasion.

Tim Ewin: Lepidodendron (giant club moss)

• Grew to a height of 30-45 metres in 10 years
• Lived 310 million years ago in swamps when Britain was located on the equator
• Formed much of the coal we use today and during industrial revolution

It would be good to bring back this species because: Lepidodendron would have a variety of practical used. It would grow rapidly in dense stands, producing a mat of rhizomes that could be used to stabilise river banks and thereby prevent flooding. It would provide a good, quick-growing source of naturally produced timber/fibre suitable for re-greening areas of felled vegetation, and it could be used as a renewable biofuel, reducing reliance on fossil sources of carbon. It could also be harvested and buried in abandoned coal mines, locking away carbon and potentially producing more coal as a source of fuel in the future (admittedly this is rather in the long term!).

Lepidodendron could also potentially be used as food for humans or livestock if it wasn’t poisonous (it probably wouldn’t be, since it evolved before specialist herbivores were common) and if it did contain toxins they may provide a source of medicines. Most importantly this ancient plant could suck lots of Carbon Dioxide out of the atmosphere and thereby limit impact of global warming, just as it did in the Carboniferous.

Depiction of a Carboniferous scene containing Lepidodendron by Mary Parrish, Smithsonian

Reasons to be careful: Hay fever – each cone produced 8000 million spores (more than grass with its meagre 2000 million pollen grains). Also, because it spreads by tiny spores that can be carried huge distances by wind, Lepidodendron could potentially be a highly invasive plant that would upset the balance of local ecosystems. It might not do so well in Britain today, since it grew in warmer environments, but in tropical areas it could potentially take over!

David Waterhouse: Mopsitta tanta (Norwegian/Danish blue Parrot)

• Most Northerly parrot (from the area of Norway and Denmark)
• Oldest fossil parrot (55 million years old)
• It could tell us how parrot-like early parrots were

It would be good to bring back this species because: This parrot is only known from a single humerus (wing bone), but because it is the oldest and most Northerly parrot it could provide a huge amount of information about the evolution, biogeography and diversification of parrots.

It would be great to know what other parrot characteristics it had – was it able to speak? Was it sociable? Did it eat fruit and nuts? Did it live in trees and nest in tree holes? Was it brightly coloured? Was it blue?

We can make sensible guesses about the answers to each of these questions (and no, it probably wasn’t blue), but without having a living or complete specimen of Mopsitta tanta we cannot be totally sure about the answers. Bringing back a specimen of something known from such fragmentary fossil material would provide an excellent test of the methods palaeontologists use to reconstruct the behaviour of extinct species.

Reasons to be careful: Ring-necked parakeets are a parrot species that were introduced to Britain through escaped and released pets. They are increasing in number quite rapidly (probably about 20,000 in the UK now) and they may become a problem for some of our indigenous species if their numbers continue to rise. Mopsitta tanta could also become established in a similar way – competing with existing species. The introduction of invasive species is the second biggest threat to biodiversity after habitat destruction, so this potential problem should be kept in mind.

You can vote for which argument you find most persuasive here:

———Results from the evening———

After a near-run first round of voting and a Harry Hill style  fight between the two favourites (pig-footed bandicoot vs Lepidodendron) an overall winner was voted for and the pig-footed bandicoot managed to grapple the right to resurrection away from the Lepidodendron (largely because Tim Ewin focussed more on the negative aspects of his species than the positive – a bit of an own goal there I think). So congratulations go to Anjali Goswami and her freaky little marsupial!

The event was good fun – the guest speakers did a great job of simultaneously entertaining and informing the audience, while the discussions and questions raised during the evening touched on some serious points. The need for stable habitats and control of invasive species were key issues that were identified, as well as the requirement for deliberate action to overcome anthropogenic environmental issues, like global warming. It would have been nice to touch upon related issues of conservation a bit more – like the Frozen Ark project by the Zoological Society of London (which is not about cloning) – but unfortunately we simply didn’t have time. If you are interested in finding out more about conservation cloning I suggest taking a look at this paper by Piña-Aguilar, et al. 2009 as a handy starting point.

We intend to run similar events in the future – I will keep you posted. Please feel free to leave comments below, including suggestions of species that you would like to see resurrected and don’t forget to explain why!