Wildlife Australia - Spring 2017

CONSERVATION OR CURIOSITY?

Among the thrills of citizen science is the possibility of discovering a new species or, better yet, the

‘rediscovery’ of a species thought to be extinct. However, an increasingly likely prospect is that genetic

technology will allow scientists to make the notion of extinction ... well ... extinct, at least for some

species. As resurrecting versions of extinct species becomes increasingly feasible, conservation genetics

researcher Helen Taylor questions whether ‘de-extinction’ can ever become a useful conservation tool.

I

magine you’re walking through the Tasmanian bush. You

hear something snuffling in the undergrowth. You pause as

a creature emerges. It’s sleek and dog-like, with pointed ears

twitching and alert, but it also has a long straight tail and tiger-

esque stripes on its back. It eyes you inquisitively, head cocked,

gives an exceptionally wide-mouthed yawn, and trots back into

the forest, disappearing between the gum trees. You’ve just

encountered a thylacine – an animal declared extinct in 1936.

This may seem an unlikely meeting, but a world repopulated

by thylacines, moa, mammoths and other long-lost creatures is

the vision of many researchers and philanthropists behind the

de-extinction movement. It’s an exciting idea that has captured

people’s imaginations, but is it feasible? If so, is it really the

futuristic conservation strategy its supporters claim we need?

We’re closer than you think

In 2009, a mountain goat kid was born via caesarean section at

a captive-breeding facility in Spain. It struggled to breathe and

died from a lung defect within ten minutes of being delivered –

sad, but not unusual in a breeding program. This was no ordinary

mountain goat; the kid was a clone of the last known Pyrenean

ibex, or bucardo – a subspecies of Spanish ibex that went extinct

nine years earlier. Scientists used skin cells taken from Celia, the

last known living bucardo, to grow clonal embryos, which they

implanted into 57 Spanish ibex and Spanish ibex goat hybrid

surrogate mothers. Only one of the resulting seven pregnancies

went to term, culminating in the tragically short life of the only

animal to be brought back from extinction so far.

The Franco-Spanish team behind bringing back the bucardo

are not the only researchers striving towards de-extinction. At the

University of New South Wales, Professor Mike Archer’s Project

Lazarus team has produced very early stage embryos of the

gastric-brooding frog, a remarkable amphibian that could turn its

stomach into a womb until the species went extinct in 1983.

In America, de-extinction devotee Professor George Church

believes he is two years away from creating an elephant embryo

that contains woolly mammoth DNA. The bucardo did not

survive, the frog embryos die a few days into development, and

an Asian elephant with a few mammoth genes is definitely not a

mammoth, but these are still significant steps towards reviving

species that we once thought were gone for good.

No facsimile

Even if de-extinction projects prove successful, they won’t create

exact copies of the species we have lost. Current pathways to

de-extinction introduce genetic information from species closely

related to the target animal into the resurrected species. The end

result looks similar, but it’s not an exact genetic copy.

The first option is to try to get back to your de-extinction target

by ‘back breeding’ existing species, aiming to create an animal that

looks like the extinct species by choosing individuals with similar

characteristics. Alternatively, you could take the route trialled with

the bucardo and the gastric-brooding frog. Take a cell from a closely

related species, clear out its nuclear DNA, fill it with DNA from

the extinct species, grow an embryo in a test tube and implant it

in the womb/egg of the closely related species. The new DNA can

come from two sources: ancient, fragmented DNA from permafrost

or museum specimens, with the gaps in the genetic code filled

in with DNA from a closely related species, or from a fully intact

genome sequenced from some kind of tissue sample preserved

before the species went extinct. Even when you don’t need to fill

in gaps in the genomes, the cell from the closely related species

CONSERVATION INNOVATION

Image: Joseph Wolf

De-extinction:

40 | Wildlife Australia | SPRING 2017