The ethics of wiping out a mosquito species

The announcement from a new genetic technology had successfully eradicated a carefully contained population of Anopheles gambiae mosquitoes grabbed headlines last week across the world. It not only indicated an incredible piece of science. It also opened a Pandora’s box of complicated ethical questions.

The technology works by creating a disruption to a particular gene found in the sex cells of mosquitoes. By manipulating something called the “doublesex” gene, the researchers were able to ensure a stream of female descendents possessing a biological mix of both male and female mosquito parts. These “intersex” mosquitoes are both genetically and phenotypically revolutionary.


Christopher Preston is the author of "The Synthetic Age: Outdesigning Evolution, Resurrecting Species, and Reengineering Our World" (MIT Press 2018). He is a professor of Philosophy and a Research Fellow in the Mansfield Center's Program on Ethics and Public Affairs at the University of Montana.

Unable to lay eggs and incapable of sucking blood, these intentionally altered females are not only much less pesky than your average mosquito. They are also wired to ensure a population crash. The genetic tool the scientists employed, known as a gene drive, permits this intersex trait to be “driven” in a few short generations through any breeding population of the species into which it is inserted. In their experiments, the scientists created a population unable to reproduce after 7 to 11 life cycles.

This powerful tool effectively permits extinction by design.

Anopheles gambiae is one of more than 3,000 species of mosquito worldwide. It is important because it is one of three that are especially deadly to humans. This lethal triumvirate are responsible for spreading malaria, yellow fever, dengue, encephalitis, zika, West Nile virus, and filariasis across vulnerable human populations.

Malaria alone, transmitted by a parasite that lives in the gut of the Anopheles species, infected 216 million people across 91 countries in 2016. It killed around 445,000 of them. Most of these deaths were in sub-Saharan Africa and most of these victims were children under the age of five.

Other efforts to limit the spread of malaria such as spraying chemicals, using bed nets, and making available anti-malarial drugs have so far proven inadequate. With climate change predicted to increase the geographical range of several mosquito species, a global public health crises of simply staggering proportions may be set to get worse.

If this is the case, why are some people hesitant about the technology?

Nnimmo Bassey of the Health of Mother Earth Foundation in Nigeria is concerned about Africa becoming a “testing ground for a technology that has not been proven.” There is no airtight guarantee about the safety of gene drives.

An intervention into an ecosystem intended to extinguish a species raises a number of precautionary red flags. Ecosystems are complex with the various dependencies between species are not completely understood. New, potentially more voracious species could fill the gaps left by those that have been removed. In the midst of any engineered changes, evolution will continue. While the particular modification the Imperial College scientists made to the mosquito was chosen specifically to minimize the possibility of a natural resistance evolving, the potential for movement and mutation of genes between populations makes people nervous. Even the research scientists themselves appreciate that wild environments don’t behave as predictably as laboratory ones.

Social as well as scientific unease is also a factor. Colonial histories raise suspicions when powerful but risky technologies developed within western nations find their initial deployments in Africa. Africans might ask whether enough is being done on other fronts in the battle against malaria.

With the human stakes so high, it is easy to think that the ethical equation is made up only of the balance between the risks and benefits for humanity. Indeed, this is likely to be the dominant part of the moral calculus.

Also in the picture, however, are questions about the kind world humans might be on the point of creating. Some will question whether it is appropriate for Homo sapiens to adopt a role in which it can command the complete elimination of another species.

One of the authors of the study, Andrea Crisanti, thinks the answer to this question is…“Absolutely, yes.” He views the malaria-carrying mosquito as a pathogen. As a pathogen, he says, “we have the right to eliminate it.”

Others think there is more here to ponder. Is it desirable for humans, rather than evolutionary forces, to determine both the species composition and the genetic make-up of the organisms that surround us? As technologies reach deeper into the surrounding world and become more precise, is it morally acceptable for humans to drive engineered changes through systems previously determined by ancient forces lying beyond our species’ reach? To some extent this means the transformation of nature into artifact.

Such a future would mark a new period in earth’s history in which one species takes up a novel role as planetary manager and designer. This species would do this consciously, deliberately, and – in the case of gene drives – quite dramatically.

Such a tightly engineered future may be inevitable. It may, in many ways, also be highly desirable.

What it shouldn’t be is a future we find ourselves immersed in without the chance to debate it, to reflect on it, and to fully understand the arguments both in its favor and against it. This is a discussion that is only just beginning.

In the meantime, hundreds of thousands of children continue to die of malaria.

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