Answer: comparative anatomy
Explanation:Darwin proposed that the forelimbs of human, bats and other creatures (whale) are similar. Although these Fore limbs are used for different purposes; he reasoned that similar forelimbs must have the same origin(Anatomy). He therefore concluded that these organisms should share same ancestors for evolution of modern Organism forms. He reasoned further that these modifications in body structures are required adaptations for survival in the competitive environment –survival of the fittest.
Charles Darwin was an evolutionist, a biologist of immense knowledge. He formulated the law of survival of the fittest