Messing with DNA — it's what we do

kw: book reviews, nonfiction, genetics, domestication, genetic engineering, sociology

DNA is practically designed to be tinkered with. It isn't hard to do. At age ten I was hybridizing tulips. I produced some pretty varieties. Then a master of DNA tinkering showed up: an infection by the Tobacco Mosaic Virus produced many "parrot" coloration varieties. Within a couple of years, things settled down, and some of the tulips went back to being the mostly solid-colored ones Mom had originally planted, plus a few of my 2- and 3-color hybrids, but some striped ones remained, apparently now breeding true to their new appearance.

Some time between 15,000 and 40,000 years ago, a subtler change occurred in an animal that hung around human encampments. Wolves had probably been stealing from garbage dumps for thousands of years already. Some, most likely younger ones, got used to continuing to gnaw on cast-off bones even if a human showed up, if the person didn't make threatening noises or moves. Did people domesticate wolves, did wolves domesticate themselves, or did both species domesticate each other? I suspect most humans were originally rather displeased about having scavengers around, so I favor the latter version. 

Whatever narrative appeals to you, at this remove of time, the main thing we know is that even very wolf-like dogs remain like juveniles. It's like dogs all have Peter Pan syndrome and never grow up. If you ever get acquainted with a wolf, as I have, you'll realize that an adult wolf is all business. Reach out a hand, and get back a stump. Make the kind of "hand-on-knees" play gesture that'll make almost any dog trot over to play tag, and a wolf will most likely fix you with a cold stare, "Seriously, human?" That's if it knows you well enough to stand there to watch your antics.

The critters we call "farm animals", "pets", and "livestock" are genetically very different from their ancestors. Cattle came from Aurochs, for example. On a camping trip I once awoke in the tent to find cattle grazing all around. I went out and swatted a few butts and said things like, "Get along now, my wife has to get up." They placidly moved on. Try that with Aurochs (you'd need a time machine), or even Bison. Your remains will soon be well mixed with mud.

Domestication and selective breeding are the traditional way to mess around with DNA. More recently we've gone from simple domestication to hyper-tinkering, still by cross-breeding and such. Your great-grandma's chicken weighed a pound and a half. Now a roasting chicken can weigh as much as eight pounds, and they cook twice as fast as a turkey of the same size, so when my wife and I have Thanksgiving alone (that may be what we have to do this year…will 2020 never go away?), we roast a chicken. But even fryers in the 3-4 pound range frequently have broken legs so frequently, because they have been bred to grow so fast their bones can't keep up.

Then there are all the plants we call "crops", plus "garden plants" and "house plants". Unless you go to the wilderness to get plants for your garden, everything in your environment has been genetically changed in the past centuries or longer. A long time ago I collected ferns for a large terrarium I made from a leaky fish tank. Forty years later I still have two or three of them. They are "wild", even thogh I keep them in "captivity". But the vegetables in one garden, and the lilies and irises and such in others, are far removed from their wild ancestors.

Dogs and domestic animals of all kinds are the backdrop to the opening chapters of Life Changing: How Humans are Altering Life on Earth by Helen Pilcher. The various kinds of selective breeding are just the start. Hybridization is another, like what I was doing with tulips, but more persistently and permanently. The mule is an ancient hybrid. Even though it is famously stubborn, it is stronger than a horse or donkey and eats less. It's the prototype of a sterile hybrid, which makes it a made-to-order animal that won't breed a herd of wild mules and take over a chunk of forest or field. Other hybrids are fertile and sometimes they settle down to become a new, stable species.

There are chapters that get into molecular engineering and genetic engineering, mainly the newest tool: CRISPR-Cas9. Humans didn't invent this tool, we discovered it. Microbes have been using it for a couple of billion years for their own purposes. It turns out that we can use it to cut-and-paste DNA however we like. Getting DNA from some cells and patching stuff in and out is pretty easy these days. The next step is harder. So hard, we're very early on the learning curve for putting the edited DNA into a working cell or a virus that can insert it into a living cell without horrible or fatal side effects. The next couple of decades ought to be interesting.

Methods more similar to the traditional interest me more. In vitro fertilization (IVF: test tube babies were the first human products, including some of my relatives) is one way to speed up the breeding process, or to cause it to happen when there are natural barriers to natural breeding (in humans, these are summed up as "infertility"). For example, IVF is being used to breed corals rapidly or to cross-breed them in an effort to produce varieties that can survive in the oceans as we expect them to be for the next couple of centuries.

That introduces another aspect of "altering life". The life we ignore, except when we go "enjoy nature" or do some "ecotouring", is being affected a lot more than we realize. Consider this: 96% of warm-blooded animals on Earth are domestic; 2/3 are birds and 1/3 are mammals. Most living birds are chickens, about 24 billion. We breed them so fast, though, that there is a total turnover about every six months because worldwide consumption of chickens is 50 billion. Cattle number about a billion. They breed more slowly; about 300 million are slaughtered for food yearly. They outweigh the chickens, probably about ten to one. Besides the space taken up by all the livestock, about half of all farmland grows crops to feed the chickens and cattle, plus swine, sheep, goats, turkeys, and so forth. The 4% of total animals that make up all the wildlife on earth have a much smaller Earth to host them.

It is heartening to read in the later chapters of efforts to "rewild" some places. The author highlights a few, such as the Knepp Estate in Sussex, England and Pleistocene Park in Siberia. Large and largish keystone species such as boars or elephants will, for free, "engineer" a landscape such that it is attractive to such a great variety of other plant and animal species, and the variety and beauty multiplies. Rare creatures (the Purple Emperor butterfly is a great example) are found at Knepp that are seldom seen elsewhere. Sturdy, Arctic-hardy horses are making Pleistocene Park better and better as a habitat for numerous small animals and the plants they favor. Mammoths, or cold-adapted Asian elephants if the Woolly Mammoth cannot be "re-evolved", would do much more to return that area to its earlier splendor.

It was such a pleasure reading this book that when the author put in a plug for her earlier book, I snapped up a copy. Stay tuned on that. In the meantime, this book is a lot more than a "gee whiz" compendium of things we can do with DNA. It emphasizes the hopeful trends that are arising. It points toward an Earth in which humans begin to play a little nicer, as we realize just how interdependent we are with "the rest of nature."