You want to bring WHAT back to life?

kw: book reviews, nonfiction, science, genetics, de-extinction

I find that it has been longer than usual since my last review. I shot myself in the foot by reading two books at the same time. It just stretched out the time for both, but it means that in another couple of days I'll have finished the second one also.

As I was reading Life Changing by Helen Pilcher I saw a footnote about an earlier book she had written, so I got that one also. This book, published in 2016, is Bring Back the King: The New Science of De-Extinction. The author worked as a cell biologist, and as a stand-up comic, so her science writing is delightfully upbeat and equally informative.

If you could choose just one extinct creature to bring back to life, which would it be? Would it be a dinosaur, à la Jurassic Park, perhaps even Tyrannosaurus rex? Or the most abundant bird of the recent past, the Passenger Pigeon? How about a Woolly Mammoth, or even a Neanderthal? These and a few others are discussed in Bring Back, with an emphasis on two questions: "Can it be done?" and "Should we do it?"

Several years ago an extinct species of goat was cloned from cells taken from the last living Bucardo while it lived. In hundreds of attempts, seven embryos were produced, and one was born but died within a minute. So the Bucardo was de-extincted for this brief moment. Animals for which living cells, or recently frozen ones, can be obtained may one day be restored by cloning.

Extensive searches for ancient DNA have been going on since before Michael Crichton wrote Jurassic Park in 1990 (the film was released in 1993; as good as it is, the book is even better). Recently, a mosquito was found in amber, with an abdomen apparently filled with its last blood meal. Of course, the delicate work of extracting some of the blood was undertaken. Nothing remotely resembling DNA or any of its constituent bases and sugars could be derived. However long the insect had been entombed, it was too long for DNA to survive.

Under the best of conditions (amber is too reactive), DNA is stated to have a half-life of about 700 years. It isn't clear what this means. Do half of the DNA strands remain pristine for 700 years, or is only half the material still recognizably derived from DNA after 700 years, or something different? Let's just consider a charitable interpretation: that half the bonds between pairs of ACGT "letters" in a strand remain unbroken after 700 years, and applying a Poisson distribution to the sizes of fragments remaining, in only a few thousand years the longest fragments would be no longer than three or four "letters", and most of the "letters", which consist of a deoxyribose sugar bonded to a base, would have broken to pieces themselves. So dinosaurs are apparently out of the question. So are Archaeopteryx, the first known bird and even Woolly Mammoths. Or so we thought. The above doesn't account for freezing.

It seems that frozen in the tundra, DNA does retain its integrity quite a bit longer, and the author reports that the entire Woolly Mammoth genome has been sequenced. Constructing the sequence had to be done by comparing snippets with the genome of an Asian elephant, to which Mammoths were closely related. 

Personally, I'd like to see Woolly Mammoths brought back somehow. So would George Church, who has determined that there are about 3 million changes in the DNA between elephant and Mammoth. Which ones are most important? Will he be able to make a set of Mammoth chromosomes and put them in the ovum of an elephant to make a Mammoth fetus and, one hopes, a baby Mammoth?

His aspiration is presently more modest: to use a subset of Mammoth DNA to make a hairy, cold-resistant elephant, what our author calls an "elemoth" (or "mammophant"). A bit of Siberian prairie called "Pleistocene Park" is waiting for the outcome. Its Russian curators have been using tanks to blunder around pushing over vegetation and small trees to simulate Mammoth activity. The other cold-adapted animals they have gathered, plus their tank-tread work, is having a salutary effect on the Park, so having real Mammoths, or mammophants, could restore a Pleistocene ecology and, they hope, reduce the effects of warming and save the permafrost.

Other candidates for restoration are more problematic. If a single passenger pigeon is produced, the species hasn't been restored. Their social life depended on living among millions of their fellows. They were prone to pretty much demolishing all the plant and insect life in an acre or two of ground, leaving behind a few hundred tons of guano, and moving on. Do we want that again? I suspect it wasn't just tasty meat and pretty feathers that doomed the passenger pigeon!

Striking closer to home, if some historical person could be cloned and raised to adulthood, could we get that person back? Consider Socrates. Getting his DNA could be problematic, because his burial place, if there is one, is unknown. More recently, who's your favorite? Washington, Lincoln, M.L. King, or even "The King", Elvis? Here the nature-nurture rubber hits the road. To get someone who is not just genetically Abraham Lincoln (plenty of his DNA is found in numerous souvenirs), but who thinks like him, is not just tricky, but onerously difficult. Would he have to grow up in a tiny cabin (I've been to his boyhood cabin in Kentucky)? Would his surrogate parents have to know and use the disciplinary methods used by Thomas and Nancy? Would there be anyone to teach him how to make a split rail fence? Would he have to study by candlelight and fireplace illumination? Do we even know all the books he read as a young person, or as an adult? How to arrange for "Nancy" to die when he is 9, so he can help construct her coffin? And on and on… And we haven't come to ethical questions; I agree with the author that these are insurmountable. We ought not try to clone Lincoln or Elvis or anyone. Not now, not ever.

In later chapters, the techniques of de-extinction are brought closer to home in another way. A few of them are already being used to increase the "birth" rate of some nearly extinct species. I call that "de-extinction before the fact". The black-footed ferret is a success story, but only in part. A disease that almost wiped out the last few colonies of ferrets is still prevalent in their home range, and so nearly all living black-footed ferrets are in captivity. Some genetic editing may be necessary to make them disease resistant. These kinds of efforts are things that should be done, yes, indeed.

Reading Bring Back the King is very enjoyable, and not just because of the frequent humor. Ms Pilcher writes delightfully, and the reading was like sitting with an old friend, listening to stories.