Final answer:
The statement is true; there have been periods in Earth's history when all continents were merged into supercontinents, the most famous being Pangaea, which existed from about 300 to 200 million years ago and was proposed by Alfred Wegener based on continental and fossil evidence.
Step-by-step explanation:
The statement is true. During the history of the earth, there have indeed been periods when all the continents were joined together in a supercontinent. The most well-known supercontinent is Pangaea, which existed approximately 300 to 200 million years ago (Ma) and included almost all of Earth's continental crust. This supercontinent eventually broke apart due to the movement of tectonic plates, and the pieces drifted to their current positions.
The configuration of Pangaea limited shallow coastal areas, which may have contributed to the Permian mass extinction, the most significant extinction event in Earth's history. The idea of continental drift was first proposed by Alfred Wegener in 1915, who observed the congruent shapes of continents and fossil evidence supporting the existence of ancient supercontinents.