Resurrection Biology: The Reality of Bringing Back Extinct Species
There has been a lot of buzz of late about bringing back extinct species like mammoths or passenger pigeons. While it might be a good idea to start thinking about these possibilities, we are years or even decades away from being able to actually pull this off with most long dead animals.
The problem isn’t reading the DNA…we are actually getting pretty good at that. And the problem isn’t even making the DNA. It would be quite a stretch to make a complete set of mammoth DNA but with a lot of time, money and effort, we could probably do it.
No, the real problem is getting a cell to read any DNA we make in the lab. See, DNA has to be folded just so to fit inside the cell and we simply cannot do this on our own yet. And when you think about the proportions of what we’re dealing with, it becomes pretty obvious why we can’t.
An animal’s DNA is stored in the nucleus inside the cell. A human has six feet of DNA in each cell and the average nucleus has a diameter of about six micrometers. So the cell manages to stuff two meters of DNA into this tiny space.
To give you an idea what we’re up against, imagine the nucleus is the size of the average baseball, almost three inches in diameter. If our nucleus were this big, we’d need to cram 75,000 feet or 14.2 miles of DNA in there. Talk about a daunting challenge!
We can’t just force it in either. We need to fold it perfectly to make sure the right genes are in the right place to be turned on properly. The DNA has to be twisted around little spools called histones and then twisted and folded and twisted some more until you get the nice compact shape of a chromosome.
Right now, only a cell can pull this off and until we figure out how to get lots of manmade DNA into a cell to have the cell fold it for us, we are stuck cloning with living or properly frozen cells. We simply don’t have this kind of material for most extinct animals. But we do have frozen cells for a few.
One likely candidate for resurrection is the Pyrenean ibex. Scientists managed to collect and save cells from the last of these wild goats before she died in 2000. These cells are now being used to try to bring this goat back.
Basically, as outlined to the right, scientists first replace the nucleus in a goat egg with a nucleus from the ibex. This won’t grow and develop properly because the ibex DNA is configured to be used by an adult cell. So the next step is to use chemicals and/or electricity to reconfigure the DNA to be useful to an embryo. Then this “fertilized” egg is grown a bit, placed in a surrogate mother goat and then, if everything goes well, the species is reborn.
So far things have not gone that well. The tricky part in this is reconfiguring the adult DNA into embryonic DNA. If this isn’t done just right, the embryo won’t develop correctly. And finding the right conditions is done by trial and error and is different for different animals. What this means experimentally is a lot of failed pregnancies and a lot of sick and dead baby goats before hitting on the right conditions.
This might be acceptable in this case to bring the goat back but maybe again it isn’t. Are lots of goats dying early, horrible deaths worth bringing back the ibex? I don’t know.
The question gets even harder when we are dealing with mammoths. Here we need to do more experimentation either because we need to try to get the DNA folded correctly or we need to get useful nuclei from cells frozen improperly in the Siberian tundra for thousands of years. Either way, we are going to have many more failed pregnancies and dead baby mammoths.
Remember, the surrogate here will be an elephant. Elephants are smaller than mammoths and have a gestation period of nearly two years.
At first the gestation period won’t matter because the failed pregnancies won’t go very long. After hundreds or thousands of failed pregnancies, scientists will have tweaked the conditions enough so that some mammoths will get closer to birth and eventually even be born. Now we’ll have to wait a couple of years to see how our new conditions worked and to make the next tweaks.
This all gets a lot more horrible if a mammoth baby is too big for an elephant to deliver naturally. If they are, we’d either need to have them born prematurely or do something like a C-section on the surrogate mother. This all sounds like a nightmare.
It was troubling enough thinking about all those dead and deformed goats but elephants are a whole different matter. In this scenario, these intelligent, caring animals are forced to endure multiple failed pregnancies and many dead babies. I am not sure how well elephants would hold up emotionally as mammoth factories.
And let’s not even go down the Neanderthal road! All these same issues would be there except we’d be dealing with near-human babies and women surrogates.
These sorts of things mean we need to really think about why we want mammoths, Neanderthals, Dodo birds or whatever. Are the benefits of resurrecting these species worth the risks to the individuals that need to carry them? And is it worth the suffering of all the individuals of that species who die an early, horrible death? There almost certainly needs to be a better reason than coolness to bring any of these animals back.
In fact, it may be best to wait until we can invent some sort of artificial womb. At least then we’d spare the pain and suffering of the surrogates.
Click here to see the key for all of these extinct species.