Final answer:
Charles Darwin and Alfred Russel Wallace independently developed the concept of natural selection, a mechanism that explains how biological change occurs over time. They observed that traits conferring a survival advantage lead to evolutionary changes in species, as discussed in Darwin's 'On the Origin of Species.'
Step-by-step explanation:
The two individuals who independently came up with a mechanism that explained biological change over time through natural selection were Charles Darwin and Alfred Russel Wallace. Darwin is renowned for his work on the Galápagos Islands, which led him to theorize that traits favorable to survival and reproduction would become more common over time, resulting in the evolution of species. This process, known as natural selection, was also independently conceptualized by Wallace based on his observations in the Malay Archipelago.
While observing various species, both naturalists recognized that those with advantageous traits would have a better chance at surviving and reproducing, leading to the gradual change in the population's characteristics. This concept was detailed in Darwin's influential book, 'On the Origin of Species,' which further elaborated on the idea of descent with modification. The cornerstone of natural selection lies in the variability of traits, the struggle for existence due to limited resources, and the inheritance of successful traits, giving rise to what we now understand as the cornerstone of evolutionary biology.