Final answer:
The most objective type of evolutionary evidence for comparing species similarity is genetic evidence, which provides clearcut numerical data like DNA sequence similarity percentages. Homologous structures and maximum parsimony are concepts used to assess evolutionary relationships based on this evidence.
Step-by-step explanation:
The type of evolutionary evidence that is most objective and allows for the comparison of clearcut numbers, such as percent similarity between two species, is genetic evidence. This evidence provides quantitative data on the similarity of DNA sequences, which can be precisely measured and expressed as percentages.
Genetic similarities are reflected in the genomic sequences, and these can be directly compared to find out how closely related two species are. Genetic evidence is more objective than morphological evidence because it deals with concrete genetic data rather than interpretations of physical form, which can lead to subjective conclusions.
Scientists apply concepts like homologous structures, which are similarities in morphology and genetics that stem from a common evolutionary path, to make evolutionary connections. The application of maximum parsimony, which suggests that the simplest explanation that coincides with the evidence is likely to be correct, helps in deciphering the pathways of evolution.