A Dim Dark Smudge by Melanie Challenger

‘Poetry can repair no loss,’ John Berger writes, ‘but it defies the space which separates.’ This year, The Clearing has commissioned seven writers to mark the Remembrance Day of Lost Species. These pieces are not eulogies. Although they respond to the grief and disorientation of our times, they are also songs of hope and memory, commitment and renewal. They mark the immensity of current and past losses, but defiantly —by bridging the ‘space which separates.’ Our sixth piece is by Melanie Challenger, who investigates the complex moral and philosophical issues around deliberate extinction. 



A Dim Dark Smudge: On the extinction of malaria-carrying mosquitoes


Queer, what a big stain my sucked blood makes
Beside the infinitesimal faint smear of you!
Queer, what a dim dark smudge you have disappeared into!

D.H. Lawrence, The Mosquito


Many people will be familiar with that high electric whine that signals the presence of a mosquito. Lying in bed in the dark, it becomes briefly audible as if you’ve tuned in and out of an alien frequency. The poet D.H. Lawrence, whose words I have borrowed for the title of this essay, called it a ‘small, high, hateful bugle in my ear,’ in his poem The Mosquito, adding in frustration, ‘Why do you do it?’ When Lawrence wrote those lines, I don’t suppose we knew enough to answer his question. Now we have a little more to go on. The hateful bugle – or ‘flight tone’ as it’s more properly known – originates in the vibration of the mosquito’s wings and forms an essential part of their mating behaviour. It’s a kind of ‘chase me’ call to the mosquito boys in the room. A study by Gabriella Gibson and Ian Russell in 2006 discovered that female mosquitoes can control the frequencies emitted by their wings and that courting mosquitoes synchronise their flight tone. More recently, Daniel Roberts’ team in Bristol studying the antennae – essentially the ears – of certain mosquito species found an extraordinary sensitivity in the animals’ hearing to nanometre-range vibrations, and sensory mechanics like the ciliated neurons – the feathery bits on some cells – to enable much greater responsiveness to particular frequencies. There’s a lot more wondrous complexity in this airborne spawning than I have space for in this essay, such is the inventiveness of evolution. But, in essence, with some remarkable pieces of anatomy and biology, male mosquitoes have very specific ways of being able to pick up and hum along with their mates. It’s a bit like tuning the radio to one person’s distant signal without any of the fuzzy interference. So, that annoying buzz on a humid night is sometimes the intimate love songs of romancing mozzies. But for us humans, who get bitten by the insects, the sound is a warning of the possibility of devastating disease.


There are thousands of species of mosquito and only a few of them pose a significant danger to human health. Aedes mosquitoes, especially Aedes aegypti with a feathery antenna reminiscent of a larch tree, are the source of diseases like dengue and Zika. Of the 400 or so species of Anopheles mosquito, around 30 to 40 are the vectors (an organism that transmits disease) of malaria. The male mosquitoes have a vegetarian diet. It’s the females, more specifically the pregnant females, who need a meal of blood before laying their eggs. Infections occur not because of the mosquito herself but rather the Plasmodium parasites carried in her body from one person to another. These parasites, which come from the waters of the breeding site, have sex inside the mosquito stomach and their offspring, as zygotes capable of moving around, burrow through the stomach wall and develop into oocysts, which break apart and release a spore-like form of the parasite that migrates to the salivary glands and is passed onto humans through a bite. These parasites then enter the liver of the unfortunate individual, later infecting the blood cells and generating both symptoms and the ability to cause further infections.


It is difficult to overstate the significance of these parasites for human lives; attempts to summarise the situation will always be impoverished. Focusing only on malaria, we can say that in 2016, the direct economic costs incurred by the affected countries of Africa was estimated at $12 billion. Statistics are notoriously difficult to obtain – especially as malaria is a febrile illness that can mimic many other illnesses – but estimates suggest as many as 800 children die each day from malaria, which is around five children in the time it might take you to read this essay. As a disease vector, the relevant mosquito species unite as the most deadly animal to humans, causing hundreds of thousands of deaths per year. We quote numbers as if this is what matters. But we are talking mostly about the deaths of loved young children who can demonstrate their desire to live and who call on us to protect them in powerful terms.


Given these deaths – which I am going to rank above the economic burden for the moment as a clear and direct consequence of diseases like malaria – it should come as no surprise that people have been discussing the possibility of driving some species of mosquito to extinction, whether locally or globally. The idea of deliberately causing the extinction of an unwanted animal is not new – and nor is it only the mosquito that is a candidate for extinction, as other pest species, including various insects that affect agriculture, are also of interest. But the possibility of extinction through gene-drive – a genetic modification of the mosquito genome such that a genetic trait is pushed rapidly throughout an entire species – has become greater in the last few years due to a technology called CRISPR cas-9.


It’s an over-simplification but basically CRISPR enables a scientist to use an enzyme (cas-9) as ‘molecular scissors’ that cut DNA in a particular part of the genome, allowing for the insertion of a change that will be incorporated as the damaged cell repairs itself. It’s intelligent mutation and it came about because scientists copied a natural mechanism that some bacteria use to defend against invading pathogens. In the past, genetic mutations have been artificially generated using chemicals or radiation. CRISPR cas-9 is a much easier and more targeted method. It is also much cheaper. It can be used for gene-drive, which pushes a gene throughout a population, or for gene-editing, which in turn can be separated into non-heritable or heritable forms. Now the extinction of unwanted animal species has gone from conjecture to a tantalising possibility. And, with it, has come a debate about the rights and wrongs of deliberately destroying a species, or of putting a lab-made genetic mutation into a wild population of animals. This debate is particularly acute because, as we all know, human actions are affecting the Earth and its systems in such a way that both the abundance and diversity of other species, including the natural rate of extinctions, are being dramatically altered, sometimes in ways that benefit a wild species but generally in ways that are reducing overall populations. This is the reality against which our decisions must rest.


Over the past few years, I have been looking into the complexities of this debate and I can tell you only one thing with confidence: it’s a huge, vigorous muddle. From the ground I can also tell you that the ethical frameworks we might use to make good choices are not currently fit for purpose. In short, science is way ahead of our values. What is more, these environmental dilemmas are going to come thick and fast over the next few decades, so it’s vital that we all contribute to the hard thinking that must be done. Looking at the case of parasites, mosquitoes, and their devastating impact can ready us for just how difficult these decisions are likely to be. I will do my best to sketch out some of the territory.


Malaria has been affecting human lives for millennia. The name originates in the Italian for ‘bad air’ and we have documents from the ancient world that speak of malarial fever without any understanding of what was causing it. Early antimalarials like quinine were discovered – or, rather, re-discovered – by Spanish missionaries in the 1600s, who witnessed some Peruvian Indian tribes using the bark of a tree now called Cinchona to treat fever. But the game-changer was the discovery of the parasites causing the disease by an overlapping group of mostly European scientists in the late nineteenth century, beginning with Charles Laveran, a French army surgeon who found parasites in the blood of a malaria patient in Algeria. What is important to understand in this brief history is that malaria was widespread in Europe, America, China, India, and elsewhere, as well as in Africa, until the twentieth century. Now over 90% of cases occur only in Africa.


I have said elsewhere that malaria is a disease of poverty as much as of mosquitoes. But that is an oversimplification. None the less, when the Americans took over from the French in building the Panama Canal at the turn of the twentieth century, it became a symbol of progress, the deep vein of world trade. But yellow fever and malaria caused tens of thousands of deaths and hospitalizations among the workers who built it until the US organised an intense and integrated program of insect and malaria control. By 1933, the tandem of economic growth and malaria elimination gathered speed in America, with the creation of a centralized body to harness the Tennessee river’s potential for hydroelectric power, industrial growth, and effective malaria management through insecticide and removal of breeding sites. Panama has incredibly rich biodiversity and abundance, as did America’s Tennessee river valley. It is hard to get good information on what was affected or lost in these developments, but it wouldn’t have been negligible. Even when the Panama Canal was upgraded recently, it was acknowledged that little was done in the way of substantial environmental impact studies. The point in all this is that malaria has been controlled or eliminated elsewhere without GM insects or heightened debates about extinction. The eradication of malaria from Europe and America, and some other regions, took place steadily and, in some cases, incidentally as these countries developed and prospered. In experiencing moral disgust at the idea of genetically-modified extinctions, we would do well to keep this in mind. In the most reductive of terms, whatever pathway we choose to remove a natural impediment will have some negative impact on wider ecosystems and other species.


The second thing to understand in the extinction debate is the real frustration of many on the frontline of the attempt to stem the deaths from malaria. In Lawrence’s poem he calls the mosquito the ‘winged victory,’ and wonders ‘who wins…Man or mosquito.’ This was a sentiment I came across commonly while interviewing a wide range of individuals involved in malaria research. Epidemiologists, doctors, scientists all spoke of ‘winning the war’ and of the exasperating ‘arms race.’ Professor Jo Lines, a parasitologist at the London School of Tropical Medicine with many decades’ worth of field experience, was eloquent on the complex effort to control malaria. ‘You had to spray longer than expected, the reservoirs were difficult to remove, and in Africa vectors were so efficient, you couldn’t quite interrupt transmission.’ Initially, there was huge success with bed-nets. These are insecticide-covered bed-nets that can have a considerable impact in reducing malaria. ‘But once coverage hopped from reasonably low to nearly everyone, insecticide resistance in mosquitoes began to shift.’


Nearly all the scientists I spoke to who had lengthy experience of working on malaria expressed scepticism that any one method would lead to the eradication of malaria or, for that matter, of the extinction of mosquitoes. In Africa, the vectors are so efficient and the biogeography is so complex and dynamic that we can’t be sure whether eradication of malaria is possible or practical. What is more, even the genetic methods come with the risk of resistance or natural mutation. As Charles Godfray, director of the Oxford Martin School reminded me, if you introduce something subject to negative natural selection, ‘You have Darwin against you. The most likely outcome is that it will disappear.’


So are the goals with regard to malaria unrealistic? A diverse range of workers I spoke with, both in Europe and in Africa, expressed their frustration at the target of eradication, which many see as unrealistic and as skewing the way in which malaria research develops – an idea born far away in the offices of funders rather than among those in the field with a real stake in how it all unfolds. The point here is that if zero cases of malaria is the research goal, then no method will work on its own. In this way, the research endeavour is incentivized towards extinction rather than management.  Another point raised among African colleagues is the question of establishing what the affected communities want. Without proper consultation, there’s a risk that African communities could see themselves as testing grounds for technologies developed in Europe or elsewhere. While university and government bioethics committees debate the rights and wrongs in the UK or the US, how do they ensure that they include good public consultation in Africa? What might shift if they discover that most individuals in these communities are holding out hope for a vaccine and better medical facilities rather than dramatic biotech solutions like GM mosquitoes?


Yet public consultation is by no means an easy process, not least because there is so much to misunderstand. When it comes to GM mosquitoes or species extinction, there are a number of potential methods, not all of which rely on gene-drive. One is a kind of animal insecticide, whereby you irradiate large numbers of mosquitoes to cause sterilisation. It would require an ongoing program to be effective, at least for a while. Using gene-editing techniques, there are two available methods: population suppression through releasing a gene for sterility or population replacement. This second possibility largely targets the means of the mosquito to defend itself against infection, by introducing modifications from other animals, such as amphibians, which have a natural resistance to Plasmodium parasites. There are advocates for each method, and plenty of reservations about each too. Some argue that replacement overcomes the extinction dilemma, and also lowers the risk of isolated populations that are resistant to sterilisation. But others argue that replacement is a slippery slope to the release of genetically-engineered invasive species. To subtilize matters further, extinctions need not be permanent. We could re-release populations of the relevant mosquitoes, especially if it was discovered they have a larger role in the food web or in pollination than imagined, once the infections of malaria had been eradicated. (Although, as one scientist pointed out, who would really want to?) Is extinction still extinction if it’s temporary? If we can undo an action, excepting unforeseen disturbances, is there anything wrong with doing it in the first place? Are all extinctions equal or can we rank extinctions on a scale that we devise? The writer David Quammen posed an interesting question to me. Would anybody mind if we sought to drive the Plasmodium parasites to extinction? These questions are reminders that ideas of moral significance often hide from sight in actions and need a fair bit of unpacking.


Public perception is very variable depending on several biases. If we are talking about saving lives, people tend to be more accepting of exactly the same technology that they might seek to ban if it was being used for solely commercial or frivolous causes. In other words, consequences matter to us. But people also react differently to the same technology depending on their feelings about the animal, i.e., whether it’s a rat or a dog. In other words, whether we like, fear or use the animal also matters to us and this is a bit harder to justify. Whatever method is used, animal testing is unavoidable, as are field tests in sites where the general population may not have been successfully consulted. What is more, for sterile release, large factories are required to develop significant enough populations of mosquitoes for deployment. And, in all this, the ethics comes into sharp focus again. Are gene-edited animals still to be categorised as wild animals or as a form of technology owned by the company? If the latter, how might this alter if a precedent is set and the regulatory framework is mobilised for use in other potential gene-drive candidates with more obviously complex behaviours like rats? While we’re still thinking through the way we treat farmed or research animals, do we want to set too many legal precedents for turning wild animals into the commercial or intellectual property of biotech companies? Are we absolutely sure of our reasoning that non-human animals only matter if they display certain capacities or if they provide ecosystems services? There are plenty of arguments in ethics that non-human species and even species and ecosystems (or ‘eco-collectives’) have intrinsic value, and, significantly, these arguments are still in development. In other words, we are currently weighing up the moral features of a decision to drive species to extinction or, relatedly, to redesigning nature for our reasons or ends. This work is not finished and arguments from continuity are not enough. By this, I mean commonly made inferences that because, for instance, we’ve bred animals, thereby changing their genetic disposition, we should not have such moral distaste about techniques like CRISPR. Morality should not be predicated on historical precedent nor should a charge of hypocrisy prevent us from re-evaluating the choices of our forebears.


In quelling fears about the likely impact of removing a species, some argue that Aedes aegypti are invasive in some places, which tends to lift any ethical queasiness. In this case, the debate is really about localised extinction, a common practice in conservation. Others argue there’s no evidence that a handful of mosquito species would have an important ecological impact, or an impact that another species couldn’t fill, but I would say there is not sufficient data at the moment to warrant that confidence. Our bias against the mosquito has made them an understudied animal from a purely ecological or behavioural perspective. One of my colleagues quipped, ‘We know more about the moon than we know about the ecology of the mosquito.’ In the case of malaria, we have to make sure a regulatory principle or a legal precedent isn’t set for a new technology without proper debate or consultation, simply because for this major application we have a large emphasis on human lives and a pathogen-bearing pest we are strongly biased against, when future uses may not have the same kind of moral sway.

Credit: Bigstock.com

None of this is easy. Are we happy tolerating a world in which there is such a disproportionate disease burden on a group of countries? How would malaria be tackled if the deaths were taking place in Europe or America? The current picture of insecticides and new vaccines or treatments are not without their own environmental ramifications or vested interests. In Africa, there is lobbying into malaria programs directly by pharmaceutical companies. Never the less, we should remain cautious about allowing economics to force our hand simply because there’s a moral vacuum on an issue. Charles Godfray made a crucial point about the concerns around species extinction. It feels worse because we know we’re doing it deliberately. It doesn’t bother us to spray mosquitoes or build out in a way that transforms ecosystems, even though these can have much greater environmental impacts than gene-drive would. Some point to this as evidence of moral bias. But the late Mary Midgley would remind us that the so-called ‘yuk factor,’ the moral disgust we experience, almost always bears greater contemplation. Mixed in with some of the irrational feelings, there might be important ideas worth closer scrutiny. The deliberateness of an act is surely one of those ideas. As the owners of our actions, are they reasonable and well-reasoned? Are the intentions good? Have we missed some glaring inconsistencies? These are questions of the general principles that inform our relationship to the world. Environmental ethicists like Paul Taylor or Holmes Rolston or Michael Nelson have been doing some hard work to hammer out these principles, but there isn’t yet a moral consensus.


We are at the foothills of the ethical dilemmas we face. We’re still not done understanding embryo testing and wastage. In our labs, we have chimeras, cerebral organoids, xenotransplantation, and huge numbers of animals still used in testing. We have people who want to de-extinct large charismatic mammals while we can’t even figure out the rights and wrongs of eating them, shooting them, or experimenting on them. All these new technologies expose an essential uncertainty in our philosophy of biology. No doubt ethicists need to address their scientific literacy, but more importantly, scientists need to address their ethical literacy. And this will be difficult if we don’t give moral philosophy the priority and the funding it needs to assist in these hugely important discussions.


And yet, in all this, let’s remember that we still have the reality of those dying children. Clearly something must be done. We want a world in which we look at every human life that is born and we value that life equally, and we all have a stake in protecting it. How we do this without ignoring the possibility that other living creatures ought not to be entirely instrumentalised by us is going to take a revolution in thought and practice. I see some hopeful signs in young activists who are putting sustainability and environmental ethics at the forefront of development. Young global leaders like Abdikadir Hassen, Mariama Mamane, Farai Mubaiwe, the team of the Global Youth Biodiversity Network or the young people wearing their black ‘We are the ones we’ve been waiting for’ T-shirts, are giving proper intellectual weight to the idea that we need different, better relationships with non-human life, with the Earth, and with each other. Perhaps we will see African countries emerge as the moral leaders of the future. As the birthplace of humanity, I hope so.


In the meantime, back to that dim dark smudge. By now it’s clear, we don’t like mosquitoes. The anger in D.H. Lawrence’s poem is both deliberate and significant. All animals we see as pests or which do, genuinely, pose an existential threat to us become the focus of emotions of disgust and aggression. The mozzie is a ‘pointed fiend’, a ‘ghoul on wings’, an ‘evil little aura,’ and its presence shakes the poet’s ‘sudden blood to hatred.’ Lawrence does what most of us would do in his situation. He thwacks the thing dead on the wall. Then comes the moment when all that anger disappears into a faint smudge of sucked blood and mosquito body. The mingled matter of a large, smart, complex mammal trying to save its children from disease, and of a tiny, hated animal trying to feed its offspring. We feel as if the rights and wrongs in all of this are easily weighed. This is why the mosquito has become the test case for the genomic control of other living species. But we’re only at the very beginning of thinking about what it means to be the hand against the wall.




MELANIE CHALLENGER is a writer and researcher across natural history, environmental philosophy and philosophy of biology. She is the author of On Extinction (2011) and of the forthcoming How To Be Animal: A new history of what it means to be human (2020).

The essays in this series were supported by the Centre for Environmental Humanities at the University of Bristol. You can find out more about their work here.  

The images in this essay are from Bigstock.com.


Join the discussion and tell us your opinion.

Anita Royreply
December 6, 2018 at 11:44 am

Brilliant, insightful and lucid essay on what is a convoluted, ethical conundrum. So much to think about, so much to learn in this. I’m looking forward to your forthcoming book. Thank you, Melanie.

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