Sunday, June 5, 2016

Ghost World - Part III: Resurrection

De-extinction. It's an amazing and controversial idea, and it may even be impossible. It's also not what you think. 

In Part I of this series, I reviewed the ways in which our world is a poor impersonation of what it was thousands of years ago, haunted by the absence of the ancient giants that once provided stability to ecosystems. In Part II, I reviewed the ways in which modern researchers are hoping to fix those ecosystems, by transporting "replacement" species to fill the gaps left by extinction, and even "un-domesticate" certain species to recreate their wild ancestors. 

Isn't there another option though? Instead of trying to replace the dead, why not bring them back? Why not simply clone extinct species?

Well, we can't. 

Well, we can, kind of. 

Well, it's complicated. 

We live in a pretty incredible time for paleontology. The discovery and study of genetic material preserved in fossils, once thought to be an impossibility, is now a regular aspect of research regarding organisms from the last few hundred thousand years. Ancient DNA has been recovered from mammoths, bison, horses, sloths, sabertooths, ancient humans, and more. Studies of this material have taught us about the lifestyles and relationships of fossil creatures in ways impossible otherwise. But can all that ancient DNA be applied to de-extinction?

Yes. Maybe. But not for cloning.

Traditional cloning is a process by which DNA is extracted from a body cell of an individual, placed into the egg cell of another individual, and coaxed to grow into an exact copy of that first animal. We did it famously with Dolly the sheep, and nowadays it is done fairly regularly. But cloning in this method requires the donation of an intact cellular nucleus, with intact chromosomes consisting of intact DNA. And that is something you simply don’t get from fossils. Even the best-preserved ancient DNA is full of missing pieces and chemically damaged fragments.

I recently read Dr. Beth Shapiro’s book How to Clone a Mammoth. In fact, that book is what inspired me to write this post, which in turn inspired me to write this whole series! In the book, she describes many of the issues facing the idea of cloning extinct species, including the issue of fragmented DNA. She even cites a number of instances where researchers attempted to use their best samples of ancient DNA for cloning efforts – all of which failed. 

Okay, so we can't "clone" ancient animals the traditional way. But surely we can use ancient genomes to re-create extinct animals, right? After all, Craig Venter and friends have been able to create bacterial genomes from scratch and insert them into living cells. Can we do the same thing with, say, a mammoth?

The answer at the moment is a resounding “maybe.” No one currently knows how to synthesize an animal genome and impart it to a living cell, although it was very recently announced that researchers want to do exactly that with the human genome. And even once we figure that out, it’s possible that we may never be able to reconstruct enough of an extinct animal’s genome to use it for “recreating” that species.

But maybe we don’t have to. 

Studies of mammoth DNA have taught us a lot about mammoths, including what features of their genetic code differ from their living relatives. These genetic differences include those features that allowed them to survive in Arctic climates. So here’s the crazy idea: using state-of-the-art techniques developed by scientists like Dr. George Church, we can edit the genome of a living animal – the Asian elephant – by inserting mammoth DNA, and create an elephant with mammoth-derived traits such as denser fur and cold-efficient blood cells. Then that “mammoth-ish elephant” can go live in that Pleistocene Park I mentioned in Part II, and make huge strides (literally) toward restoring the ecosystem balance of the past!

This is the closest living relative of the woolly mammoth: the Asian elephant.
Some rewilding proponents have suggested introducing elephants to Northern continents,
but perhaps a dose of mammoth DNA would improve their chances?
Image from Wikipedia.
This crazy idea is entirely within the realm of possibility, and is being considered not just for mammoths, but for more recent victims of extinction such as the passenger pigeon. The results would not be “clones” of extinct species, nor really extinct species at all. Instead these would be modern species making use of “extinct genes” to take the place of their ancient relatives. As described in Part II, modern species may be used to complete fractured ecosystems in places like Europe and North America, but in cases where the modern options can’t quite cut it, some assistance from ancient DNA might be an incredibly valuable tool.

Of course, there are problems. Consider these questions:
- Will these edited genomes be viable?
- If so, where do we grow those embryos? There’s no such thing as a “test-tube baby.” A baby mammoth – whether it’s fully mammoth or just a slightly edited elephant – needs a womb to grow in. Can a modern elephant’s womb carry an edited baby? 
- Will that baby develop properly in that foreign womb?
- Who will raise that baby? It will be unique, unlike any species alive. Is any living being qualified?
- Where do these "de-extincted" animals live? Will they even be able to survive in the habitats we want to preserve?

The answers to these questions, and many more, are unknown for now, and much more research needs to be done before we can answer them. We may find that this crazy idea is actually an impossible idea. Some researchers seem to think so. If it is, I’m sure we’ll learn a lot along the way. If it isn’t, then the Pleistocene Rewilding dream of restoring a semblance of Ice Age ecosystems will be one huge step closer to being reality, complete with our very own modern version of mammoths and other long-lost creatures.

Shapiro 2015. How to Clone a Mammoth.

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