If an intelligent alien species landed on the small bit of galactic rock that we call home, they might get out of their spaceships, have a look around, and decide that we—that is, our species—are the master builders on our planet. There would be plenty of reasons to think so. We build bridges spanning enormous waterways, aptly named skyscrapers, and stadiums that seat tens of thousands. And that doesn’t even scratch the surface of the diversity of structures we build: schools, airports, apartment buildings, shopping malls, a Starbucks on every corner.
But we’re not the only species that modifies the environment to suit its needs. Some animals simply set up shop in pre-existing spaces, like bears that spend the winter hibernating in natural caves. Some can build a home by simply moving around an impressive amount of dirt, like gophers and ants. Some animals, however, create more elaborate spaces, transforming their environment in the process. If a group of aliens did land on our planet, they would just have to look a bit harder to see it.
Secrets of the Universe: Past, Present, FutureX