What If We Weren’t the First Advanced Civilization on Earth?

In the grand sweep of Earth’s four-billion-year history, 300 years is barely a blink. And yet, that blink — our industrial era — has already reshaped the atmosphere, oceans, and sediments. If civilization collapsed tomorrow, would anything of us remain 100 million years from now? Could some alien beings visiting Earth in the future ever tell that this planet was inhabited by an advanced civilization? More startling still: if another civilization once existed on Earth long before us, could we even tell?