This episode explores the palaeogeography of Earth over millions of years, and its impact on the development of life on the planet. Tyson starts by explaining that the lignin-rich trees evolved in the Carboniferous era about 300 million ago, then explains on the nature of plate tectonics that would shape the landmasses of the world and the asteroid impact that initiated the Cretaceous–Paleogene extinction event, leaving small mammals as the dominate species on earth. Earth's landmasses are expected to change in the future and postulates what may be the next great extinction event.

The series ‘Life on Our Planet’ brought to life by Steven Spielberg and narrated by Morgan Freeman, unfolds the remarkable and epic four-billion-year journey of life on Earth. Its captivating narrative explores the continuous battle of life to conquer and survive, delving into the history of the 20 million species that exist today. However, what we witness is merely a snapshot in time; 99% of Earth's inhabitants are buried in our deep past. This series weaves the tales of these dynasties, chronicling their rise and fall in a story that is as incredible as it is enlightening, sparking a profound interest in the history and resilience of life on Earth.
The first episode traces the evolution of life on our planet and highlights the diversity of life, from ancient sharks to the reign of dinosaurs and the emergence of mammals. The episode showcases the constant struggle for survival and adaptation across different eras, illustrating the dynamic and often brutal nature of Earth's evolution.

Moving on to the Late Eocene period 36 million years ago and mammals have prospered and are now the largest creatures on land and sea. This is an era of animals like andrewsarchus, the biggest mammal carnivore ever to walk on land, and the brontotheres, small-brained herbivores. It is in the sea, however, that the most monstrous mammals of all can be found. We follow the fate of a female basilosaurus, a huge serpent-like early whale, but nothing like the gentle filter feeding whales of the 21st century. Four times the length of the great white shark, with jaws to match, she is every inch a killer.