Final answer:
Natural selection being accepted as the driving force of evolution required an understanding of genetics, recognition of gradual evolution, and a shift in societal and religious attitudes.
Step-by-step explanation:
In order for natural selection to be accepted as the driving force of evolution, several key developments were required. First, there needed to be an understanding of the mechanisms of inheritance, which was achieved through the discovery of genetics and the integration of genetics and evolution in the modern synthesis. This provided a clear explanation of how variation in traits is passed down through generations and how natural selection acts on this variation to drive evolution.
Second, there needed to be a recognition of the gradual nature of evolution. Initially, the prevailing theory of blending inheritance made it difficult to understand how gradual evolution could occur. However, with the advent of the particulate nature of genes and the understanding of how genetic variation arises through mutation, the concept of gradual evolution became more widely accepted.
Lastly, there needed to be a shift in societal and religious attitudes towards the acceptance of evolution. While many scientists and naturalists had already embraced the theory of evolution, it took time for the wider public and religious leaders to come to terms with the idea that evolution and natural selection could coexist with religious beliefs.