Life grows through stages, with earlier stages serving as the foundation for later stages. Thus, a human being begins as a child, goes through adolescence, and becomes an adult, and a butterfly starts as an egg, becomes a larva, pupates, and then becomes an adult. Such is the same for the history of life. Although strict creationists might maintain the earth is but 6,000 years old, the reality is that it is billions of years old. And the foundation for modern life is tied to the foundation of the Carboniferous, 300 million years ago.
Indeed, even humanity's energy sources today are tied to the Carboniferous, since most of the world's fossil fuels—coal, oil, and natural gas—were formed during that period. The Carboniferous coal beds provided much of the fuel for power generation during the Industrial Revolution and are still of great economic importance, providing the source to produce most of the world's electricity. From a Unificationist aspect, these fossil fuels are a valuable natural resource that God has provided us with. Yet, the history of their use has often been tied to the poorer aspects of humanity, such as unsafe and unhealthly conditions for miners, pollution, and so forth.