It seems that every time I retrieve a magazine from my mailbox these days, I find an article about how we’re going to drive mosquitoes to extinction. The June issue of Smithsonian’s featured, “A World Without Mosquitoes” and the August National Geographic proclaimed, “Science vs. Mosquitoes” (it’s not hard to guess who wins). Through the technological wonder of CRISPR-Cas9 combined with gene drive, we’re told that we can insert a gene to confer sterility and this trait would race like wildfire through Aedes aegypti. Why this species? Because it’s the vector of the Zika virus—along with the dengue and yellow fever viruses. The problem is that A. aegypti isn’t the only culprit. It’s just one of a dozen or more bloodsuckers that will also have to be wiped out. After we’ve driven these species to extinction, we’ll presumably move on to the Anopheles species that transmit malaria. That’ll be another 40 extinctions, but once we have the technology rolling it should be readily applicable to all sorts of pests. But let’s slow down for a moment and ask a few questions about the new genetic technology before we start intentionally reshaping life on Earth (we’ve been wiping out species for some time, but most of these losses are the collateral casualties of habitat destruction).
Can we drive targeted species to extinction?
Well, maybe. We chuckle at those who told budding entomologists to be sure to collect specimens of pests because DDT would soon eliminate all sorts of insects. The evolutionary power of insecticide resistance was unimagined in the 1940s. Perhaps we are being equally unimaginative with CRISPR as a method of extinction. After 30 years of working in pest management, my money is on the insects. Although I’m not sure how they’ll humble us this time, they’ve outfoxed our technological prowess up until now. But let’s suppose I’m a poor gambler.
Should we drive species to extinction?
There are those who advocate wiping out vectors entirely. But this seems like overkill, so to speak. Why eliminate an entire species—along with all of its ecological functions, most of which we don’t know? It seems much more sensible to eliminate the capacity of the species to spread disease (technically speaking, insects transmit pathogens and the pathogens cause disease, so vectors don’t’ really “spread disease” but “spread disease-causing agents” is awkward and you know what I mean). Researchers at Harvard Medical School used CRISPR to remove all 62 occurrences of retroviruses embedded in the porcine genome which make using pig organs unsuitable for transplantation to humans. So why not wipe out a few mosquito genes rather than the whole species? But let’s suppose that we decide for forge ahead.
How do we decide where to stop?
Reshaping genomes to fit our needs is the first step. Then comes redesigning life to accord with our wants: our desire for noiseless cicadas (they can be so disruptive), stingless honeybees (no reason to put up with their bad attitude), or poop-less aphids (nobody likes honeydew and sooty mold on their shiny car). And why stop at a world without vector mosquitoes? Surely, we’ll wipe out the nuisance species that afflict us with itchy bumps. And fleas can go, along with cockroaches, locusts, ticks, starlings, rats, and raccoons (I’ve been battling these garden invaders for years). Okay, some people will want to keep raccoons. So how do we decide where to stop—and who gets to decide for the rest of us? But let’s suppose that I’m a worrywart and we figure out what goes and what stays.
What else might we eliminate along with genes and species?
Much has been written by philosophers for 2500 years about what it means to be human. Beginning with the Greeks, a great deal of discussion has revolved around the virtues which give meaning to our existence. These are the character traits which we cultivate in an effort to realize our potential, to lead a good life, and to become fully human. There are various candidates for the virtues, such as courage, mercy, justice and fidelity. But most frameworks include some version of temperance. A life worth living entails self-control and moderation. Perhaps the modern formulation would be humility—understanding that we are not the sole end of existence, that human comfort is not the purpose of life on Earth, and that our wants can be trumped by others’ needs. I am concerned about an arrogant restructuring of organisms and ecosystems, but I’m most deeply worried about what this means for human morality. We can easily reshape genetic traits of other species, but can we preserve the character traits of our own species?
Featured image credit: Electron microscope image of Zika virus (red), isolated from a microcephaly case in Brazil. Image by NIAID. CC-BY-2.0 via Wikimedia Commons.