Final answer:
Scientists in the late 18th and early 19th centuries began to realize and theorize about evolution as evidence showed that life forms have changed over time.
Step-by-step explanation:
By the late 18th and early 19th centuries, scientists began to realize that evidence showed life forms have changed over time and started theorizing about evolution. Georges Cuvier's observations of fossilized remains led Jean-Baptiste de Lamarck to hypothesize that organisms adapted to their environment by changing over time. Charles Darwin's theory of evolution by natural selection eventually became the most accepted explanation for the changing life forms on Earth.