Biologist Leonard Brand conducted experiments with newts to evaluate claims about what?

Leonard Brand's experiments with newts were focused on evaluating claims related to evolutionary changes in newt populations. Specifically, Brand sought to address the idea that certain newt populations exhibit varying traits over time, potentially supporting the theory of evolution by natural selection. His research provided insights into how environmental factors and genetic variations influence adaptations within these populations of newts.

The other options, while related to the study of amphibians, are not the primary focus of Brand's work. For instance, the idea of footprints in sandstone pertains to geological interpretations rather than biological claims about newts. Similarly, habitat preferences involve ecological aspects that are not the central theme of Brand's experimental designs. Lastly, while coloration in mating displays is a relevant topic in behavioral ecology, it does not directly align with the evolutionary claims that Brand was investigating. Thus, his work was specifically geared towards understanding evolutionary processes in newt populations.