Paul Thomas is a pioneer in mouse research. His lab is in Adelaide, at the South Australian Health and Medical Research Institute, a sinuous building covered in pointy metal plates. (Adelaideans refer to the building as the “cheese grater”; when I went to visit, I thought it looked more like an ankylosaurus.) As soon as a breakthrough paper on CRISPR was published, in 2012, Thomas recognized it as a game changer. “We jumped on it straightaway,” he told me. Within a year, his lab had used CRISPR to engineer a mouse afflicted with epilepsy.
When the first papers on synthetic gene drives came out, Thomas once again plunged in: “Being interested in CRISPR and being interested in mouse genetics, I couldn’t resist the opportunity to try to develop the technology.” Initially, his goal was just to see if he could get the technology to work. “We didn’t really have much funding,” he said. “We were doing it on the smell of an oily rag, and these experiments, they’re quite expensive.”
While Thomas was still, in his words, “just dabbling,” he was contacted by a group that calls itself GBIRd. The acronym (pronounced “gee-bird”) stands for Genetic Biocontrol of Invasive Rodents, and the group’s ethos might be described as Dr. Moreau joins Friends of the Earth.
“Like you, we want to preserve our world for generations to come,” GBIRd’s website says. “There is hope.” The site features a picture of an albatross chick gazing lovingly at its mother.
GBIRd wanted Thomas’s help designing a very particular kind of mouse drive—a so-called “suppression drive.” A suppression drive is designed to defeat natural selection entirely. Its purpose is to spread a trait so deleterious that it can wipe out a population. Researchers in Britain have already engineered a suppression drive for Anopheles gambiae mosquitoes, which carry malaria. Their goal is eventually to release such mosquitoes in Africa.
Thomas told me there were various ways to go about designing a self-suppressing mouse, most having to do with sex. He was particularly keen on the idea of an “X-shredder” mouse.
Mice, like other mammals, have two sex-determining chromosomes—XXs are female, XYs male. Mice sperm carry a single chromosome, either an X or a Y. An X-shredder mouse is a mouse who’s been gene edited so that all of his X-bearing sperm are defective.
“Half the sperm drop out of the sperm pool, if you like,” Thomas explained. “They can’t develop anymore. That leaves you with just Y-bearing sperm, so you get all male progeny.” Put the shredding instructions on the Y chromosome and the mouse’s offspring will, in turn, produce only sons, and so on. With each generation, the sex imbalance will grow, until there are no females left to reproduce.
Thomas explained that work on a gene-drive mouse was going slower than he’d hoped. Still, he thought by the end of the decade someone would develop one. It might be an X-shredder, or it might rely on a design that’s yet to be imagined. Mathematical modeling suggests that an effective suppression drive would be extremely efficient; a hundred gene-drive mice released on an island could take a population of fifty thousand ordinary mice down to zero within a few years.
“So that’s quite striking,” Thomas said. “It’s something to aim for.”
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If the Anthropocene’s clearest geological marker is a spike in radioactive particles, its clearest biological marker may be a spike in rodents. Everywhere humans have settled on the planet—and even some places they’ve only visited—mice and rats have tagged along, often with ugly consequences.
The Pacific rat (Rattus exulans) was once confined to Southeast Asia. Starting about three thousand years ago, seafaring Polynesians carried it to nearly every island in the Pacific. Its arrival set off wave after wave of destruction that claimed at least a thousand species of island birds. Later, European colonists brought to those same islands—and to many others—ship rats (Rattus rattus), thus setting off further waves of extinctions, which are still ongoing. In the case of New Zealand’s Big South Cape Island, ship rats didn’t arrive until the 1960s, by which point naturalists were on hand to document the results. Despite intensive efforts to save them, three species endemic to the island—one bat and two birds—disappeared.
The house mouse (Mus musculus) originated on the Indian subcontinent; it can now be found from the tropics to very near the poles. According to Lee Silver, author of Mouse Genetics, “Only humans are as adaptable (some would say less so).” Under the right circumstances, mice can be just as fierce as rats, and every bit as deadly. Gough Island, which lies more or less midway between Africa and South America, is home to the world’s last two thousand pairs of Tristan albatrosses. Video cameras installed on the island have recorded gangs of Mus musculus attacking albatross chicks and eating them alive. “Working on Gough Island is like working in an ornithological trauma center,” Alex Bond, a British conservation biologist, has written.
For the last few decades, the weapon of choice against invasive rodents has been Brodifacoum, an anticoagulant that induces internal hemorrhaging. Brodifacoum can be incorporated into bait and then dispensed from feeders, or it can be spread by hand, or dropped from the air. (First you ship a species around the world, then you poison it from helicopters!) Hundreds of uninhabited islands have been de-moused and de-ratted in this way, and such campaigns have helped bring scores of species back from the edge, including New Zealand’s Campbell Island teal, a small, flightless duck, and the Antiguan racer, a grayish lizard-eating snake.
The downside of Brodifacoum, from a rodent’s perspective, is pretty obvious: internal bleeding is a slow and painful way to go. From an ecologist’s perspective, too, there are drawbacks. Non-target animals often take the bait or eat rodents that have eaten it. In this way, poison spreads up and down the food chain. And if just one pregnant mouse survives an application, she can repopulate an entire island.
Gene-drive mice would scuttle around these problems. Impacts would be targeted. There would be no more bleeding to death. And, perhaps best of all, gene-drive rodents could be released on inhabited islands, where dropping anticoagulants from the air is, understandably, frowned upon.
But as is so often the case, solving one set of problems introduces new ones. In this case, big ones. Humongous ones. Gene-drive technology has been compared to Kurt Vonnegut’s ice-nine, a single shard of which is enough to freeze all the water in the world. A single X-shredder mouse on the loose could, it’s feared, have a similarly chilling effect—a sort of mice-nine.
To guard against a Vonnegutian catastrophe, various fail-safe schemes have been proposed, with names like “killer-rescue,” “multi-locus assortment,” and “daisy-chain.” All of them share a basic, hopeful premise: that it should be possible to engineer a gene drive that’s effective and at the same time not too effective. Such a drive might be engineered so as to exhaust itself after a few generations, or it might be yoked to a gene variant that’s limited to a single population on a single island. It has also been suggested that if a gene drive did somehow manage to go rogue, it might be possible to send out into the world another gene drive, featuring a so-called CATCHA sequence, to chase it down. What could possibly go wrong?
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While I was in Australia, I wanted to get out of the lab and into the countryside. I thought it would be fun to see some northern quolls; in the photos I’d found online, they looked awfully cute—a bit like miniature badgers. But when I asked around, I learned that quoll-spotting required a lot more expertise and time than I had. It would be much easier to find some of the amphibians that were killing them. So one evening I set out with a biologist named Lin Schwarzkopf to go toad hunting.
As it happened, Schwarzkopf was one of the inventors of the Toadinator trap, and we stopped by her office, at James Cook University, to take a look at the device. It was a cage about the size of a toaster oven, with a plastic-flap door. When Schwarzkopf turned on the trap’s little speaker, the office reverberated
with the toad’s thrumming call.
“Male toads are attracted to anything that sounds even remotely like a cane toad,” she told me. “If they hear a generator, they’ll go to it.”
James Cook University is situated on the northern Queensland coast, in the region where the toads were first introduced. Schwarzkopf figured we should be able to locate some toads right on the university grounds. We both strapped on headlamps. It was about 9 p.m., and the campus was deserted, except for the two of us and a family of wallabies hopping about. We wandered around for a while, looking for the glint of a malevolent eye. Just as I was beginning to lose heart, Schwarzkopf spotted a toad in the leaf litter. Picking it up, she immediately identified it as a female.
“They won’t hurt you unless you give them a really hard time,” she said, pointing out the toad’s toxin glands, which looked like two baggy pouches. “That’s why you shouldn’t hit them with a golf club. Because if you hit the glands, the poison can spray out. And if it gets in your eyes, it will blind you for a few days.”
We wandered around some more. It had been so dry, Schwarzkopf observed, the toads were probably short on moisture: “They love air-conditioning units—anything that’s dripping.” Near an old greenhouse, where someone had recently run a hose, we found two more toads. Schwarzkopf flipped over a rotting crate the size and shape of a casket. “The mother lode!” she announced. In about a quarter-inch of scummy water were more cane toads than I could count. Some of the toads were sitting on top of one another. I thought they might try to get away; instead, they sat there, unperturbed.
The strongest argument for gene editing cane toads, house mice, and ship rats is also the simplest: what’s the alternative? Rejecting such technologies as unnatural isn’t going to bring nature back. The choice is not between what was and what is, but between what is and what will be, which, often enough, is nothing. This is the situation of the Devils Hole pupfish, the Shoshone pupfish, and the Pahrump poolfish, of the northern quoll, the Campbell Island teal, and the Tristan albatross. Stick to a strict interpretation of the natural and these—along with thousands of other species—are goners. The issue, at this point, is not whether we’re going to alter nature, but to what end?
“We are as gods and might as well get good at it,” Stewart Brand, editor of the Whole Earth Catalog, famously wrote in its first issue, published in 1968. Recently, in response to the whole-earth transformation that’s under way, Brand has sharpened his statement: “We are as gods and have to get good at it.” Brand has co-founded a group, Revive & Restore, whose stated mission is to “enhance biodiversity through new techniques of genetic rescue.” Among the more fantastic projects the group has backed is an effort to resurrect the passenger pigeon. The idea is to reverse history by rejiggering the genes of the bird’s closest living relative, the band-tailed pigeon.
Much closer to realization is an effort to bring back the American chestnut tree. The tree, once common in the eastern United States, was all but wiped out by chestnut blight. (The blight, a fungal pathogen introduced in the early twentieth century, killed off nearly every chestnut in North America—an estimated four billion trees.) Researchers at the SUNY College of Environmental Science and Forestry, in Syracuse, New York, have created a genetically modified chestnut that’s immune to blight. The key to this resistance is a gene imported from wheat. Owing to this single borrowed gene, the tree is considered transgenic and subject to federal permitting. As a consequence, the blight-resistant saplings are, for now, confined to greenhouses and fenced-in plots.
As Tizard points out, we’re constantly moving genes around the world, usually in the form of entire genomes. This is how chestnut blight arrived in North America in the first place; it was carried in on Asian chestnut trees, imported from Japan. If we can correct for our earlier tragic mistake by shifting just one more gene around, don’t we owe it to the American chestnut to do so? The ability to “rewrite the very molecules of life” places us, it could be argued, under an obligation.
Of course, the argument against such intervention is also compelling. The reasoning behind “genetic rescue” is the sort responsible for many a world-altering screwup. (See, for example, Asian carp and cane toads.) The history of biological interventions designed to correct for previous biological interventions reads like Dr. Seuss’s The Cat in the Hat Comes Back, in which the Cat, after eating cake in the bathtub, is asked to clean up after himself:
Do you know how he did it?
WITH MOTHER’S WHITE DRESS!
Now the tub was all clean,
But her dress was a mess!
In the 1950s, Hawaii’s Department of Agriculture decided to control giant African snails, which had been introduced two decades earlier as garden ornaments, by importing rosy wolfsnails, which are also known as cannibal snails. The cannibal snails mostly left the giant snails alone. Instead, they ate their way through dozens of species of Hawaii’s small endemic land snails, producing what E. O. Wilson has called “an extinction avalanche.”
Responding to Brand, Wilson has observed, “We are not as gods. We’re not yet sentient or intelligent enough to be much of anything.”
Paul Kingsnorth, a British writer and activist, has put it this way: “We are as gods, but we have failed to get good at it…We are Loki, killing the beautiful for fun. We are Saturn, devouring our children.”
Kingsnorth has also observed, “Sometimes doing nothing is better than doing something. Sometimes it is the other way around.”
1
A few years ago, I received a sales pitch, via email, from a company offering a new service to those concerned about their role in wrecking the planet. For a price, the company, called Climeworks, would scrub subscribers’ carbon emissions from the air. Then it would inject the CO2 a half a mile underground, where the gas would harden into rock.
“Why turn CO2 into stone?” the email asked. Because humanity had already emitted so much carbon “that we have to physically remove it from the atmosphere to keep global warming at safe levels.” I immediately signed on, becoming a so-called “pioneer.” Every month, the company sent me another email—“your subscription will renew soon and you will continue to turn CO2 emissions into stone”—before billing my credit card. After a year of this, I decided it was time to visit my emissions, an admittedly reckless move that swelled my emissions still further.
Though Climeworks is based in Switzerland, its air-into-rock operation is situated in southern Iceland. Once I got to Reykjavík, I rented a car and drove east along Route 1, the ring road that circles the country. After about ten minutes, I was clear of the city. After about twenty, I was beyond the suburbs, racing across an ancient lava field.
Iceland is essentially all lava field. It sits atop the Mid-Atlantic Ridge, and, as the Atlantic Ocean widens, it’s being pulled in opposite directions. Running diagonally across the country is a seam lined with active volcanoes. I was headed toward a spot near the seam—a three-hundred-megawatt geothermal plant known as the Hellisheiði Power Station. The landscape looked as if it had been paved by giants and then abandoned. There were no trees or bushes, just clumps of grass and moss. Squarish black boulders lay jumbled in heaps.
When I arrived at the gate of the plant, the whole place seemed to be steaming and the air stank of sulfur. Soon a cute little car drove up, painted in bright orange. Out of it climbed Edda Aradóttir, a managing director at Reykjavík Energy, which owns the power station. Aradóttir is blond and bespectacled, with a round face and long hair that she was wearing pinned back. She handed me a hard hat and put one on herself.
As power stations go, geothermal plants are “clean.” Instead of burning fossil fuels, they rely on steam or superheated water pumped from underground, which is why they tend to be sited in volcanically active areas. Still, as Aradóttir explained to me, they, too, produce emissions. With the superheated water inevitably come unwanted gases, like hydrogen
sulfide (responsible for the stink) and carbon dioxide. Indeed, pre-Anthropocene, volcanoes were the atmosphere’s chief source of CO2.
About a decade ago, Reykjavík Energy came up with a plan to make its clean energy even cleaner. Instead of allowing the carbon dioxide to escape into the air, the Hellisheiði plant would capture the gas and dissolve it in water. Then the mixture—basically, high-pressure club soda—would be injected back underground. Calculations done by Aradóttir and others suggested that deep beneath the surface, the CO2 would react with the volcanic rock and mineralize.
“We know that rocks, they store CO2,” she told me. “They’re actually one of the biggest reservoirs of carbon on earth. The idea is to imitate and accelerate this process to fight global climate change.”
Aradóttir opened the gate, and we drove in the little orange car to the back of the power station. It was a breezy day in late spring, and the steam rising from the pipes and cooling towers seemed unable to make up its mind which way to blow. We paused at a large metal-clad outbuilding attached to a structure resembling a rocket launcher. A sign on the building said: Steinrunnið Gróðurhúsaloft, which was translated as “greenhouse gas petrified.” Aradóttir told me that the rocket launcher was where the power station’s CO2 was separated from other geothermal gases and prepared for injection. We drove on a bit farther and came to what looked like an outsized air conditioner stuck onto a shipping container. A sign on the container said: Úr Lausu Lofti, or “out of thin air.”
This, Aradóttir said, was the Climeworks machine that was scrubbing my emissions—really, just a fraction of my emissions—from the atmosphere. The machine, formally known as a direct air capture unit, suddenly started to hum. “Oh, the cycle just started,” she said. “Lucky us!
“At the beginning of the cycle, the equipment sucks in air,” she went on. “The CO2 sticks to specific chemicals inside the capture unit. We heat up the chemicals and that releases the CO2.” This CO2—the Climeworks CO2—is then added to the club-soda mixture from the power plant as it makes its way to the injection site.
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