De-extinction
hopes to revive mammoths, gastric frogs and other missing species, but it might
undermine the conservation of creatures that still survive
By David
Biello | Tuesday, March 19, 2013, Scientific America
WASHINGTON, D.C.—The rebirth of an extinct
frog species may come from the freezer, not the stomach. The gastric
brooding frog, when it existed on Earth, swallowed its eggs, transformed its
stomach into a womb and vomited up its young once sufficiently grown. But the
frog disappeared from the mountains of southern Australia shortly after it was
discovered in the 1970s, persisting only as a few frozen specimens in the
bottom of a scientist's freezer.
The cells in
those tissues should have been ruptured by the swelling ice crystals
that formed within and around them. But some of the cells remained reasonably
intact, according to paleontologist Michael Archer of the University
of New South Wales in Australia, who
is attempting to resurrect the species via his Lazarus Project. He and his
colleagues transplanted the nucleus of that cell and others like it into
hundreds of eggs from a closely related species. "Last February we saw a
miracle starting to happen," Archer announced for the first time to the
crowd at the TEDx De-Extinction event on March 15 at the National
Geographic Auditorium. "One of them began to divide." (Archer’s group
has not published the work yet.)
While tadpoles
may be a long way off, let alone a viable frog, the southern gastric brooding
frog might be the first species brought back from the dead permanently.
The first de-extinction happened in 2003, although it lasted all too
briefly. Scientists coaxed a clone of an extinct ibex from Spain to birth
from a special hybrid goat. But the cloned bucardo bore a third lung
and couldn't breathe properly, dying within 10 minutes.
Although this
early effort failed, the growing cohort of resurrection projects raises a
central question: Does extinction mean forever, anymore? If not, do we have an
obligation to bring species back? "If it's clear that we exterminated
these species, we not only have a moral obligation to see what we can do about
it but a moral imperative to do something if we can," Archer argued. The
new science of synthetic biology aims to make it possible for him to
fulfill that moral imperative.
Humans have
killed off many species, both iconic and common. A lighthouse keeper's cat
Tibbles—aided by a few feral cats perhaps—caught and killed nearly every
single Stephens
Island wren just as
they were discovered by science in 1900. Hungry sailors ate the Steller's
sea cow to death within a century of its discovery. The Xerces Blue
butterfly disappeared with the sand dunes from San Francisco in the 1940s as that city
swelled. The American chestnut, once the most abundant tree in eastern
North America, succumbed to a fungal blight imported from Asia
by humans.
"As a
human species, we have been amazingly efficient at making things
extinct," noted conservation scientist Kate Jones of University
College London at the TEDx DeExtinction event.
As the
extinction rate swells thanks to habitat loss, over-hunting and human-induced
climate change, the world may be on pace to lose half of all species by the end
of this century—a reality dubbed the sixth extinction because it
would represent the sixth mass die-off of life in Earth's history. Of course,
the other five were caused by climatic, planetary or astronomic events.
The
de-extinction effort is being led by a group of scientists and others, ranging
from synthetic biologist George Church of Harvard Medical School to
environmental gadfly Steward Brand of the Long Now Foundation and its Revive
& Restore project. They have banded together to see if new genetic tools
might enable them to bring back even more species, as Archer is attempting to
do with the gastric brooding frog. Their first target is the passenger pigeon,
which once was so abundant it darkened the skies of eastern North
America.
A similar bid
by scientists in South Korea
to revive the woolly mammoth—an even more scientifically challenging feat
because it has been extinct for thousands of years—may garner the most
attention, however. And no need to stop there; extinct human species, like the
Neanderthal, could be revived as well, or even sabre-tooth cats—although
species that have been extinct for more than a few thousand years are unlikely
to be found preserved with enough DNA intact to permit their restoration.
(Say goodbye to Jurassic
Park.)
As the bucardo
example shows, however, de-extinction will be no easy feat. For the bucardo,
scientists will not only need to get a female clone to survive, they will also
need to find a Y chromosome to make a male bucardo and then stitch that into
the cloned DNA. Another approach, championed by Robert Lanza of Advanced Cell
Technology, is to forego cloning and instead create stem cells from
the ancient DNA. That would then enable Lanza or other scientists to create
sperm or egg cells that bear the DNA of endangered or extinct species—and can
provide the genetic code to restore or resurrect them.
Going from DNA
to a stem cell of some kind, that is then coaxed into becoming a sperm or egg
cell, and finally grows into a mammoth, however, is a process still beyond even
the most advanced genetic science. "You cannot realistically change one or
10 percent of a genome and have that go to term," Lanza noted in an
interview with Scientific American, which is the reason for multiple
implantations when attempting to impregnate. But "this is the beginning.
It's not going to stop."
Furthermore,
as paleogenomicist Beth Shapiro of the University
of California, Santa Cruz, reminded the TEDx audience,
creating an embryo is just the first step in bringing any extinct species back.
There is also the mammoth challenge of restoring the world—or at least the
ecosystems—that the elephant relatives inhabited, among other hurdles. And
given the perilous plight of still extant elephant species, humanity has yet to
show that it can manage the survival, let alone the revival, of a pachyderm.
Still, there
are lessons to be learned from the mammoth, not least the importance of cold.
The Arctic "is the best place for the long-term
preservation of DNA," Shapiro said. "It's cold and it's been cold for
at least the last million years."
Just as
mammoth DNA has waited in the Siberian tundra, preserved by constant cold
temperatures, the cold of the San
Diego's frozen zoo may be the key to
ensuring that today's biodiversity makes it through the next few centuries of
the Anthropocene intact. This ark, maintained at a steady -197
degrees Celsius, holds the cells of 503 mammals, 170 birds, 70 reptiles and 12
amphibians and fish—out of an estimated 10 million animal, plant, microbe and
fungal species on the planet. The collection displays a bias toward charismatic
megafauna and thus against the uncharismatic microfauna that keep the planet
alive. The cold Svalbard seed vault in Norway performs the same function
for crops—species that, despite their importance to us, have dwindled in
biodiversity as genetic engineering has created specialized variants that now
dominate the landscape.
Some conservationists
also pour cold water on the very idea of de-extinction, worrying that it could
enable the extinction of yet more species by diverting funds from proven
efforts to sustain them, such as protected areas, intensive management of small
surviving populations, even advertising campaigns to reduce the consumption of
endangered species. We might bring the mammoth back while letting its relatives
slip away. "At this moment, brave conservationists are risking their lives
to protect forest elephants from armed poachers," noted biologist
David Ehrenfeld of Rutgers
University at TEDx.
"And we're talking in this safe auditorium about bringing back the woolly
mammoth?"
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