Final answer:
During Darwin's time, influential geologists like James Hutton and Charles Lyell contributed to the understanding that Earth was old. Their works on uniformitarianism and the immense geologic time scale necessary for the processes they observed had a significant impact on Darwin's development of the theory of evolution.
Step-by-step explanation:
During Darwin's time, geologists like James Hutton and Charles Lyell were suggesting that Earth was old. Lyell, in his work Principles of Geology, championed the theory of uniformitarianism, which posited that the slow-acting geological forces of the past are the same as those in the present.
Therefore, to account for the significant geological changes observable in the landscape, the Earth had to be much older than the few thousand years that were commonly believed at that time based on biblical calculations. These ideas greatly influenced Charles Darwin, leading him to consider the slow process of evolution in the context of a much more ancient Earth, providing the time necessary for the wide array of species diversification observed.
Without the understanding of Earth's great age, Darwin may have struggled to conceptualize the gradual nature of evolutionary change. The geologic time scale introduced by Hutton and popularized by Lyell was pivotal for the foundation of Darwin's evolutionary theory.