Sahotra Sarkar, PhD
Professor of philosophy and integrative biology
University of Texas, Austin
Gene drives constitute the most important technological advance in molecular biology since the advent of PCR in 1983. They allow an introduced gene to be propagated through a population at a much faster rate than ordinary inheritance based on Mendel’s rules. If this gene causes carriers to become sterile, the population is driven to extinction. If, through migration or other factors, the gene is also introduced in other populations of the species, they also become extinct. In many cases, the species would be driven to extinction.
Should we do this? For a species such as Aedes aegypti — the main vector of dengue, chikungunya and Zika, and the only important vector of yellow fever — forced extinction through the introduction of a gene that turns all carriers male seems not only permissible but even compelling. So far, conventional vector-control methods have not been successful; that is why yellow fever persists and dengue was (until Zika) the most rapidly spreading mosquito-borne disease in the world. Gene drives would finally achieve what these methods have failed to accomplish.
Yet, for many philosophers and biodiversity conservationists, such a policy choice would be unethical. For some, all species have a right to exist or, at the very least, we have no right to drive them to extinction. Their critics within these disciplines would deny any such rights exist. However, many of them would still find a policy of enforced extinction troubling. They wonder about the wisdom of causing extinction.
The end of A. aegypti may not spell the end of any of these diseases. For instance, a second mosquito species, A. albopictus, is known as a vector of dengue and chikungunya, although not as efficiently as A. aegypti; it is also a highly likely vector of Zika. Should we also drive A. albopictus to extinction? What if some other species gets implicated as a vector? Must it follow the first two into oblivion? Where do we draw a line?
Should we stop at disease vectors? Should we not also target the many undesirable invasive species that have destroyed local ecologies throughout the world? What if the introduced gene then infects native populations of these species and drives them to extinction globally? In all these cases, what about unintended ecological consequences? Gene drives are supposed to be partly reversible, but reversion still leaves species with permanently altered genomes. Is that acceptable?
These difficult questions underscore how important it is to have a structured public discussion and debate about gene-drive policy. Until that debate is settled, and reasonable standards are established as public policy, it would be unwise to recommend gene drives to drive any species to extinction. The sooner the discussions and debates start in the public arena, the better prepared we will be to face future problems such as the ongoing Zika crisis.
Disclosure: Sarkar reports no relevant financial disclosures.