Zombie Dodos and Pigeons and Mammoths, Oh My!

A stranger thing that's been going around the science news lately (and around science for a decade or two) is the idea of de-extinction, or bringing back currently extinct animals:

That sounds so cool, right?  Do it!

Well, maybe not so fast.  Like any act of 'playing God,' this kind of thing could have serious and unintended consequences.  Just ask Dr. Ian Malcolm.

However, before we get too excited, we need to make a few things clear.

• Jurassic Park won't be happening anytime soon.  Why?  Well, DNA has a half-life of 521 years, which means that after 521 years under normal conditions, half of the DNA sequence will be gone.  After 521 more years, half of the remaining half will be gone, and so on.  Scientists have estimated that the farthest back we could go with DNA would be a few hundred thousand years under ideal conditions.  Therefore, dinosaurs aren't the focus here.
• More broadly, we need DNA to recreate anything.  If there aren't samples that have at least somewhat retrievable DNA, we won't be able to bring it back (unless we use the less exact method of selective breeding, which I'll discuss below).
• I'm not going get into whether this the right thing or not to do.  That is a philosophical debate more than anything, with legitimate arguments on both sides.  But the 'cool' factor is pretty powerful.
• We've actually already done it. (???)  That's right, we have, a decade ago, when a group of scientists brought back from extinction the bucardo, an ibex species in Spain and France, which had gone extinct in 2000.  However, the little bucardo that was born had an extra lobe on its lung and died after only ten minutes.  So, for ten minutes in 2003, we had de-extincted the bucardo.

So, how exactly does this work?  Simply enough, actually (in theory).  Let's assume that you have a full or nearly-full DNA sequence contained in a surviving cell.  You find yourself a suitable host (which can be difficult if the creature has no close relatives) and take an egg from the host.  You then scoop out the DNA of the egg and replace it with the extinct animal's DNA.  Then you implant it into the host.  Lather, rinse, repeat, and hope one of them sticks.  For that poor little bucardo who ended up dying, they tried 57 different hosts.  Only seven had successful implantations, and only one of those carried to term.

Now, that raises the question.  What happens if we can't find a suitable host?  Some extinct animals, such as the woolly mammoth, the passenger pigeon, and the buscardo have close relatives that are still living (Asian elephant, band-tailed pigeon, and domestic goat, respectively).  Others, such as the Tasmanian Tiger, the dodo, or the giant sloth, may prove more difficult (though for a dodo, you'd probably just need a big enough egg, which may not be that hard to procure).

Alternatively, suppose we have a host (such as an Asian elephant), but we are still struggling to find a full DNA sequence (such as the woolly mammoth).  In that case, I don't quite know what happens.  In Jurassic Park, there's that goofy video where they say they've replaced DNA holes with frog and lizard DNA.  I'm not a scientist, so I'm not sure if you can do that.  You probably can do something like it, though.  However, if they could use the soft tissue from mammoth remains to get a full DNA sequence, that would be just plain awesome.

And that's generally the situation we're in right now.  We're trying to patch together sequences of DNA to get a complete sequence from long-dead species.

One of the other de-extinction methods (though I don't think this one is really what it claims to be) is, by selective breeding, to reverse-engineer an extinct animal.  The most notable of these is the Tauros Project, which seeks to bring back the aurochs, the ancestor of the modern cow.  This is made possible because (a) the species only went extinct in 1627 and (b) there are many, many old breeds of cattle, which, genetically, are very similar to the aurochs (for example, see the image below, which shows the male and female of many breeds of cattle, with the aurochs at the bottom):

However, does that mean that a reverse-engineered aurochs would be an aurochs?  I don't think so...I think it would just be a cow that looks like an aurochs.  But, as I already mentioned, I'm not a scientist.

For a good discussion from a TED Talk on the state of de-extinction, check this one out:

Assuming this can actually happen, here's my top five list of animals that absolutely need to be brought back from the dead:

1. Woolly Mammoth - luckily, this one is actually pretty likely.  There are tons of examples of soft tissue and hair, which may contain full DNA sequences.  Plus, we have Asian elephants, which would be great surrogates.  However, shockingly, we've never harvested elephant eggs before, so that's kind of a hangup right now, beyond the DNA issue.
2. Tasmanian Tiger - We have videos of the thing, so know a lot about it.  We also have samples of it (I think).  I hope someone's working on this one, since it would be a cool, weird animal.  It also only went extinct in 1936.
3. Saber-toothed Cat - Really any of them (since there are a few different species).  It would just be way too cool to see how one of these things eats and whatnot with the ginormous teeth.  I haven't heard anything about anyone trying to bring this one back, though.
4. Dodo - Does this even need an explanation?  It's a dodo, people.
5. Baiji - This poor little river dolphin recently went extinct (like, in 2004), which is totally sad.  There aren't enough river dolphins in the wild.  There should be more.

Honorable mentions go to the Passenger Pigeon, the Carolina Parakeet, the Great Auk, and the Giant Sloth.

I really want to see this thing happen.  For reals, y'all.