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“Jurassic Park” for the birds?
This photo shows Martha (right), an extinct passenger pigeon, at the
Smithsonian's Natural History Museum in Washington, D.C. Once the
most plentiful bird on the planet, the passenger pigeon became
extinct in September 1914 when Martha died at the Cincinnati Zoo.
Photo: AP Photo/Susan Walsh
The last lonely bird of a species that once numbered 3 billion died in 1914. Martha, as she was known, had
been the last passenger pigeon since her mate George died in 1910. The last living member of a social species,
she lived out her days alone in a cage in the Cincinnati Zoo. Her preserved corpse can now be seen at the
Smithsonian Institution
But what if the passenger pigeon could be brought back?
After all, specimens of long-dead animals still contain DNA, genetic material that can be thought of as a set of
instructions on how to form a particular species. Packets of DNA combine to form genes associated with
a particular trait. If enough of those genes can be recreated, perhaps a long-gone species could be brought
back to life.
That's the idea behind something called de-extinction.
It works like this: Take DNA harvested from specimens stuffed in museum drawers, like Martha. Figure out
which genes matter and then use genetic engineering to edit the DNA of a closely related species into some
version of the extinct species. If all goes well, a copy of the long-lost Martha could be born and, one day,
flocks of passenger pigeons could be restored.
Getting The Genes To Fit
Ben Novak is doing pioneering work to make this exact scenario come true. Novak's effort is focused on
acquiring genetic information from stuffed passenger pigeons, while simultaneously studying the genetic
makeup of the closely related band-tailed pigeon.
So far, 32 passenger pigeon samples have had their genomes sequenced. "Genome" is simply the word for the
complete set of genes found in an individual animal, while "sequencing" refers to the process of figuring out
the order of the genome's parts — that is, the order of its DNA bases. Just as the words in a sentence need to
be in a certain order to make sense, so too do DNA bases need to be ordered in a particular way for genetic
information to be conveyed. A unique sequence is what creates an animal's particular genetic profile.
All of Novak's passenger pigeon samples come from birds killed between 1860 and 1898. "That's right in the
range when the bird was going extinct," he notes.
Novak has also been helped by outside efforts, including the nearly complete sequencing of three passenger
pigeons. The genes of those three individuals show that passenger pigeons have been through population
booms and busts before — their numbers have grown and shrunk at different times.
Passenger pigeons have gone through times in their evolutionary history when their numbers were
quite small, geneticist Beth Shapiro said. That suggests that scientists may be able to create a small population
of pigeons that can grow on its own.
Birds Of A Feather
"All of our birds," Novak adds, "are all very, very similar to each other — like everybody being cousins,
essentially — which is the effect of this recent rapid population expansion." Novak and his team are
interested in figuring out when that population expansion happened.
To figure out when the last boom occurred will require finding DNA from fossil samples thousands of years
old. Novak has already begun to examine a few such samples. If the population explosion happened more
than 400 years ago, then it is unlikely that the European arrival in North America caused the boom that
produced billions of birds, as some have suggested.
With ancient samples and those from the 19th century, Novak and others could begin to figure out how the
bird lived in the wild. Understanding how the passenger pigeon existed makes it more likely people could
bring the bird back and have the species thrive in the woods available today. There is "nothing in the data so
far to shout at us to turn back now and not bring back the passenger pigeon," Novak says.
Novak's team has not yet completed the band-tailed pigeon sequencing required to begin resurrecting the
passenger pigeon. However, experiments with cells from the band-tailed pigeon may begin as soon as next
year. The work would be similar to experiments now being done to see if the woolly mammoth can be
resurrected, brought back to life, through its still-living relative, the Asian elephant.
Early Birds Have To Learn
If the de-extinction works, the only remaining challenge would be to teach the new birds how to be passenger
pigeons. Doing that would likely be even more challenging than the genetic work itself. To understand the
difficulty, look at similar efforts — such as attempts to raise California condors with puppets or to teach
cranes to migrate by using ultralight airplanes.
Still, if everything goes well, birds that carry the genes of the passenger pigeon could be flapping around by
the end of the decade.
The project may prove too ambitious, however. Similar efforts that stretch back 30 years have so far failed to
produce a quagga, an extinct species of zebra. Likewise, the 2003 experiment that resurrected a bucardo for
seven minutes has yet to be repeated. Nevertheless, conservationists are examining how the science used for
de-extinction might be used to preserve endangered animals and plants or bring them back if they die out.
There are advantages, however, to working with an animal that is already extinct. The scientists don't exactly
have to hurry. After all, Martha died 100 years ago. "If we succeed, the world gets a new" kind of bird, Novak
says. "If we fail, we learn things that are valuable and the world isn't left with another extinct species."