Johnathan Blair / National Geographic

A museum worker inspects a replica of a woolly mammoth, a species that went extinct 3,000 to 10,000 years ago. In March 2012, scientists in Russia and South Korea announced a partnership to try to clone the mammoth and generate a living specimen.

If scientists can use genetic engineering to bring back the woolly mammoth, should they do it? How about the passenger pigeon? Or the western black rhino? Do we humans have a responsibility to restore at least some of the species that our ancestors wiped out? And if we bring them back, will they really be the same?

Such questions are the focus of TEDxDeExtinction, a public forum that's being presented on Friday from 8 a.m. to 5 p.m. ET at National Geographic's Washington headquarters. You can watch the whole thing online via LivestreamTEDx and National Geographic's De-Extinction website, which also has loads of articles and resources on the issue. The event has been organized by Revive & Restore, a nonprofit clearinghouse for worldwide de-extinction work that's under the aegis of the Long Now Foundation in San Francisco.

"De-extinction"? What's that?

"It's using new technologies like cloning and genome sequencing to reconstruct a species that went extinct," science writer Carl Zimmer explained. Zimmer's talk at Friday's TEDx event will help set the scene for the de-extinction debate, and he's also written a cover story on the topic for National Geographic's April issue.

National Geographic

National Geographic's cover story for the April issue focuses on the prospects of reviving ancient species.

De-extinction has been in the works for more than a decade, basically ever since Dolly the Sheep demonstrated in 1996 that mammals could be cloned from cells in a lab dish. Spanish and French scientists worked for years on an effort to bring the Pyrenean ibex back from extinction, by cloning cells that had been preserved from the last known animal of the species. They succeeded only in producing a deformed kid that died 10 minutes after birth.

That brief de-extinction (and re-extinction) took place in 2003 and was reported in 2009. Since then, significant advances have been made in cloning and in other technologies for DNA sequencing and gene splicing. That's allowed scientists to think about what previously was unthinkable. Russian and Korean researchers, for example, are looking through the tissue of a woolly mammoth that was preserved in the deep freeze of Siberia's permafrost, in hopes of finding cells that are suitable for cloning.

Harvard geneticist George Church, meanwhile, is working on a technique for inserting snippets of reconstructed DNA code from an extinct species into stem cells for a closely related living species. The coding for the traits of a passenger pigeon could be reintroduced, bit by bit, into a breed of common rock pigeon. Over the course of many generations, the rock pigeons would become more and more like passenger pigeons.

"George Church's method will open up a whole new range of possibilities," Zimmer said. "You're not actually grabbing an intact molecule that was inside an animal that was alive 1,000 years ago."

This type of reverse engineering could also open up a whole new range of questions. "Is a regular rock pigeon that's been given the traits that passenger pigeons had really a passenger pigeon, or is it a hybrid, or whatever?" Zimmer asked.

In a similar vein, plant researchers are sorting through the genome of Asian chestnut trees, with the intention of picking out the specific strings of DNA coding that can make American chestnuts more resistant to a species-killing fungus. The trick could save American chestnut trees from extinction, even though it's debatable whether they'd still be American chestnuts. "It's not the original thing, it's better," Zimmer said. "But should be we be doing that?"

It's not such a giant leap to think about looking through the Neanderthal genome as well, to find out whether it contains the coding for traits that could make humans "better." Church's reflections on that subject sparked all sorts of exaggerated reports a couple of months ago, replete with references to Neanderthal babies being spawned by human surrogate mothers-for-hire.

Zimmer said the last thing that Church and his colleagues want is a genetic free-for-all over de-extinction. "They want this to be something where there's a strong consensus," he said. "This is not an off-the-reservation project."

Friday's event could represent a significant step toward building that consensus. Watch the webcast and see for yourself. National Geographic's webcast portal includes the day's schedule.

Photographer Joel Sartore, one of the scheduled speakers at TEDxDeExtinction, has been documenting species on the brink of extinction for his Photo Ark project. Here are three of the species he has included in his portfolio. For more about Sartore, check out this Daily Nightly blog posting:

Joel Sartore / National Geographic

The golden pheasant (Chrysolophus pictus) is a species native to mountainous forests of western China.

Joel Sartore / National Geographic

The striking panther chameleon (Furcifer pardalis) is native to tropical forests of Madagascar. The reptile is highly prized by collectors for its bold colors and relatively large body size (up to 9 inches or 23 centimeters long).

Joel Sartore / National Geographic

The Mexican gray wolf (Canis lupus baileyi) is the most rare subspecies of gray wolf in North America. It is listed as critically endangered by the IUCN.

More about the genetic frontier:

• How synthetic biology will change us
• Potentially endless line of mice cloned
• Extinct tiger gene resurrected in a mouse

The de-extinction issue is due to be addressed in a one-hour National Geographic Channel special, "Mammoth: Back From the Dead," premiering April 12. Also, the Wildlife Conservation Society is planning a conference April 9-11 in Cambridge, England, on the implications of synthetic biology for conservation.

Alan Boyle is NBCNews.com's science editor. Connect with the Cosmic Log community by "liking" the log's Facebook page, following @b0yle on Twitter and adding the Cosmic Log page to your Google+ presence. To keep up with Cosmic Log as well as NBCNews.com's other stories about science and space, sign up for the Tech & Science newsletter, delivered to your email in-box every weekday. You can also check out "The Case for Pluto," my book about the controversial dwarf planet and the search for new worlds.