February 28, 2020, by Brigitte Nerlich

Gene drives and Trojan horses: A tale of two metaphor uses

I was reading a recent article on gene drive entitled “Engineering bugs, resurrecting species: The wild world of synthetic biology for conservation” and came across this sentence about a so-called ‘Medea drive’: “This genetic Trojan Horse could then be used to spread elements that confer susceptibility to certain environmental factors, such as triggering the death of the modified fruit flies at a certain temperature.”

This reminded me of two things: the strong presence of Greek myths in biology/genomics and the frequent use of ‘Trojan horse’ in discourses about gene editing and gene drive (also cancer research and elsewhere). Think about Pandora, Prometheus, Icarus, not to speak of biological nomenclature! In our case, a Medea drive is named after “the character in Greek mythology that killed her offspring”. In this blog post I’ll focus on the Trojan horse metaphor, which, interestingly, is not explained or paraphrased in the article.

It is assumed that people know the backstory to this metaphor, that is to say, the Trojan war, the siege of Troy, the ‘gift’ of a wooden horse, which was let into the besieged town but turned out to be full of soldiers, who then conquered Troy. They also are supposed to know that metaphorically a ‘Trojan horse’ “has come to mean any trick or stratagem that causes a target to invite a foe into a securely protected bastion or place”, and to have probably come across or be fearful of a computer virus called a Trojan horse. It should be stressed that knowledge of Troy and the horse is rather culture specific. So this metaphor only works against the backdrop of a certain type of cultural knowledge.

The explanatory use of the Trojan horse metaphor

The use of the Trojan horse metaphor in biology/genomics is less well known but seems to have become quite popular in recent years, especially in the context of CRISPR, genome editing and gene drive research.

Genomes can be edited (modified, changed) in many ways. The most recent and most easy way is to use CRISPR. This is a tool based on a natural process used by bacteria to protect themselves against viruses, which can now be used by humans to identify, cut and modify specific DNA sequences in genomes. In this process harmless viruses can be used as ‘Trojan horses’.

As an ethical review of genome editing by the Nuffield Foundation on Bioethics explained: “it may be possible to use a vector (e.g. a virus) as a kind of Trojan Horse to introduce genome editing tools to make the necessary repairs within the patient’s body”. And here is a passage from an article on CRISPR that uses this metaphor, detailing the use of a “small, harmless helper virus called AAV, well-suited for carrying genetic instructions into a living cell. AAV won’t make you sick, but it can still sneak into your cells and hijack their machinery, making them a perfect Trojan horse in which to put good stuff—like a correct copy of a gene”…

Now, gene drives sneak more into a cell than normal gene editing tools. A gene drive doesn’t just edit a DNA sequence using CRISPR trickery; it hijacks the way inheritance functions. It is a genetic modification designed to spread through a population at higher-than-normal rates of inheritance. As one article said, referring to the pioneering work of Austin Burt at Imperial College London, one can “use these ‘super-Mendelian’ genes as a Trojan horse, to rapidly distribute altered DNA, and thus ‘to genetically engineer natural populations’”. Exploiting this super-Trojan-horse trickery, gene drives can be used not only to treat individuals but to manipulate (in effect eradicate) whole populations, of, for example, mosquitoes transmitting malaria.

In this context, two of the most quoted passages are perhaps these ones (more research needed!): “Researchers from London’s Imperial College have employed a Trojan Horse-like form of genetic engineering in a lab setting to wipe out a population of malaria-transmitting mosquitoes in less than 11 generations.” And: “’We want to build a Trojan horse in the mosquito,’ says [Omar] Akbari [UC San Diego]. “When a mosquito is infected by a virus — whether it’s dengue, Zika, chikungunya, yellow fever, whatever — it activates our system, which kills the mosquito.’”

Here the Trojan horse metaphor is used as an explanatory device, to explain how a cell is ‘tricked’ into doing things it would normally not do, such as eliminating disease carrying insects, agricultural pests or invasive species.

However, the Trojan horse metaphor is also used to talk about another sort of trickery. And here we come to a political, rather than scientific, use of the Trojan horse metaphor.

The accusatory use of the Trojan horse metaphor

In November 2018 a UN Convention on Biological Diversity conference took place in Egypt. This was just the time when gene drives were being discussed more widely in the press.

The ETC Group, a civil society group that monitors the impact of emerging technologies, participated in this conference. As they pointed out before the conference, 20 years ago they protested against genetically modified seeds they called ‘Terminator’ or ‘suicide’ seeds. In 2018 they protested against what they called ‘child of Terminator’ or an ‘Exterminator’ technology, namely the new genetic tool that is ‘gene drive’.

In this context they used the Trojan horse metaphor: “The biotechnology industry has learned from their first attempt to foist the terminator on the world. In Egypt, they will not speak out, but present instead their Trojan horse, called Target Malaria – a $100 million project from Imperial College in London, UK”. (The ETC Group also uses the Trojan Horse metaphor in their critique of geoengineering; a comparison between geoengineering and gene drive metaphors might be interesting in general….)

Friends of the Earth also took this conference as an opportunity to draw attention to what they called an ‘extinction technology’ and said about Target Malaria: “This Trojan horse project is exploiting a public health crisis in Africa, despite the lack of underlying science to support its efficacy as a sound medical intervention”.

This was quoted in one of only three articles I could find in the news data base Nexis talking about gene drive and Trojan horse. The other two say that “a coalition of activist groups compared gene drives to the atomic bomb and accused researchers of using malaria as a Trojan horse to cover up the development of agricultural gene drives for corporate profit”.

There is a fear then that saying gene drive will be used for the benefit of people (eliminate malaria), is an underhand ploy or trick to do other things: sideline better approaches to dealing with malaria or, on the back of this use of what one can call ‘medical gene drive’, introduce ‘agricultural gene drive’ that will only profit large corporations not the people on the ground, similar to past GMOs.

While the accusatory metaphor ways made it into the mainstream media, the explanatory Trojan horse metaphor did not, it seems. This might be indicative of what Dietram Scheufele said in one of the articles referring to activists’ use of the Trojan Horse metaphor: “scientists are generally much worse than activist groups at shaping public opinion, in part because they tend to rely on logical reasoning and facts, while activist groups are more likely to tap into unconscious values and emotions”.

This means that the explanatory metaphor seems to lose out to the accusatory metaphor in the context of wider gene drive communication activities.

The analytical use of the Trojan horse metaphor

So far, social scientist, like the mainstream media, have not really picked up on the explanatory use of the Trojan horse metaphor, focusing instead on the accusatory one.

Phil Macnaghten and others have studied seminal narratives used by people to form views and attitudes towards emerging technologies. Such narratives are, for example, the ‘slippery slope’ narrative, which implies, they say, “that technological advances that seem beneficial now will inevitably evoke further technological steps and applications that are morally doubtful”, and the ‘Trojan Horse’ narrative, which implies “that innovations developed for progressive purposes will in the long term have unforeseen and potentially irreversible effects”. Gene drive discourses seem to draw on this narrative.

Another use of the Trojan horse metaphor highlighted by social scientists is that of legitimising problematic uses of gene drives. One article published last year (referencing another published in 2017) points out that “the use of this technology to control certain invasive species, if successful, could become a Trojan horse to legitimize the eradication of other species without questioning to whom or what they are harmful”. As we have seen, some critics of gene drive use this narrative.


The Trojan horse metaphor seems to have two uses when communicating gene drive. It is used to explain one aspect of the science of gene drive (here the metaphor is quite neutral in terms of evoking emotions),  and it is used to criticise the potential uses of gene drive in society (here it is negatively charged); it has what I called an explanatory and an accusatory function. Both metaphor uses rely on the story of ‘trickery’. In one use, a cell is framed as being tricked into doing things, which might be good or bad. In the other use, people are framed as being tricked into doing bad things or bad things are legitimised or seen as creeping in under the radar.

Is this a metaphor with a split personality? On the one hand being used in the context of the public understanding of gene drive science and on the other in the context of the public understanding of gene drive applications and implications? Can this lead to confusion? Or are the contexts sufficiently different for this not to happen?

Image: Trojan horse, Wikimedia Commons

Posted in biotechnologygene drivegenomicsLanguageMetaphorsScience Communicationsynthetic biology