Traveling is extremely arduous for microscopic sperm -- think of a human trying to swim in a pool made of...other humans.
David Attenborough visits archaeological sites where fossils were found illustrating the origins of life on earth, in the ocean. For long, evolution worked very slow and species remained primitive, mostly single-cell, alter fractal. Only the invention of sexual reproduction kick-started genetic diversification.
There is no greater test for life than winter, as temperatures plummet to 70 below and winds reach 200kph. Darkness and ice extend across the polar regions and only a few remarkable survivors gamble on remaining. We join a female polar bear trekking into the Arctic mountains to give birth as the first blizzards arrive. Out on the frozen ocean, the entire world's population of spectacled eider ducks brave the winter in a giant ice hole kept open by ferocious currents. Arctic forests transform into a wonderland of frost and snow - the scene of a desperate and bloody battle between wolf and bison, but also where a remarkable alliance between raven and wolverine is made. Beneath the snow lies a magical world of winter survivors. Here tiny voles dodge the clutches of the great grey owl, but cannot escape the ultimate under-show predator - the least weasel. Midwinter and a male polar bear wanders alone across the dark, empty icescape. Below the snow, polar bear cubs begin life in an icy den while fantastical auroras light the night skies above. In Antarctica, we join male emperor penguins in their darkest hour, battling to protect precious eggs from fierce polar storms. Weddell seals escape to a hidden world of jewel-coloured corals and alien-looking creatures but frozen devastation follows as sinister ice stalactites reach down with deadly effect.
The leatherback sea turtle is a magnificent creature that can be found in Atlantic, Pacific, and Indian Oceans. This ancient species swims faster, travels further, and dives deeper than any other reptile on the planet. In the Atlantic, they migrate every year from their nesting grounds in the Caribbean to the chilly waters off the east coast of Canada where they feast on jellyfish. This epic annual journey – at a staggering 12,000 km – is the longest for any reptile in the world.
The Serengeti is one of the most biologically diverse areas on earth--but it's also the scene of some of the most important fossil discoveries ever made. Join us as we meet the modern inhabitants of this ancient land, and track how their evolution helped shape our understanding of human origins.