The trolley problem is a classic philosophical dilemma, and its variants have been used extensively to test moral intuitions. Scanning the brain of human subjects with functional MRI during task performance has proven useful to understand how emotion and reason interact when we ponder bioethical issues. It would be interesting to adopt those approaches to study the psychological barriers towards controversial innovations such as gene drives. Just imagine you alone are responsible for pressing a button and switching on gene drives in malaria-spreading mosquitoes. Someone is going to die, and you must decide whom to save.

If you do nothing, malaria will continue to kill 445.000 people every year. If you press the button, a species will go extinct. This thought experiment is particularly interesting now that Andrea Crisanti’s team at Imperial College London has crashed caged populations of the malaria vector Anopheles gambiae in only 7-11 generations, overcoming resistance issues previous attempts have faced. They targeted doublesex, a gene that controls whether an insect will be male or female. By altering this gene, females develop intersex characteristics, fail to bite and do not lay eggs. Think of this genetic switch as your trolley dilemma button. I would press it without hesitation to end the malaria scourge. What would you do?