The provided text from the YouTube video "The Invisible Barrier Keeping Two Worlds Apart" on the PBS Eons channel explains the Wallace Line, a biogeographic boundary that separates the animal life of the Malay Archipelago. The line is a result of plate tectonics and the collision of two ancient continents, Sunda and Sahul. While the continents are close now, they were once separated by deep waters and strong currents, which prevented the exchange of species between them. This has resulted in a distinct contrast in the animal life on either side of the line, with Asian species found to the west and Australian species found to the east. The line is an example of how ancient geological events can continue to shape the diversity and distribution of life today.