Winter had lasted eighty thousand years when, in a very short time, an immense forest began to grow, rapidly covering the entire planet. This new planetary configuration involved real transformation linked to the cycle of the seasons, changes in the habitat and the evolution of flora and fauna. After taking us around the globe on the routes of migratory birds and crossing the oceans with whales, Jacques Perrin and Jacques Cluzaud take us on a journey through time to rediscover the entire European region, an environment that we have shared with wild animals since the end of the Ice Age.