2of3 - Miracle Planet (Part03) New Frontiers - Onto the Land

New Frontiers: Onto the Land
Episode 3 tells the story of how "continental drift" brought our ancestors onto the land. Four hundred million years ago, shallow seas around primeval continents were home to most life-forms. The size of the shallow seas decreased as the supercontinents, like Laurasia formed. Some species found freshwater homes inland to escape from a struggle for survival in the ocean. Continental drift caused the formation of huge mountains. The peaks blocked atmospheric currents, creating clouds that rain. The rain gathered to make rivers at the foot of the mountains. Our ancestor, Eustenopteron, came to live in those rivers at the foot of the Caledonian mountains, where primeval trees called Archaeopteris developed a mild and stable environment. The leaves of Archaeopteris supplied nutrients for life, but caused oxygen depletion during dry seasons. Eustenopteron and other fish species developed proto-lungs to survive in low oxygen. Huge predators appeared as well. Acanthostega sought to hide from predators in Archaeopteris branches that piled in water near riverbanks. They made their way forward by pushing the branches aside, thus developing a forefoot. After several million years, Pederpes finally made the first step onto the land.