<p>The model organism approach in neuroscience promises to yield insights into the workings of the human brain and reveal general principles of nervous system structure and function. Yet its success depends on the representativeness of the model organisms studied. If model organisms are representative of species beyond themselves, they can provide a suitable basis for reliably extrapolating findings to humans and other organisms. However, model organism selection in neuroscience is rarely optimized for representativeness, and instead primarily reflects other considerations such as cost, convenience, and historical convention. This is especially true for model organisms repurposed from other scientific domains, where organisms are ported from one experimental context to another based on a previous track record of success combined with the availability of associated methods and research infrastructure. Consequently, many studies in neuroscience provide a weak foundation for extrapolation. After discussing this widespread issue in neuroscience, I suggest that the way forward involves more careful attention to comparative data and insights about biological evolution.</p>