In our own species history, human has kept for ages an arrogant and presumptious attitude towards nature. Human race has been feeling the dominant species of all living form, and of its environment. We have to analyze life´s history, to understand which the human role in Earth must be. Since the cell life was born in Earth, Symbiosis was established as a principal evolutive mechanism: Mutual cooperation in all life levels favours the adaptations to environment and survival of living species. When the human race appeared on Earth, the symbiotic role was principal; however, with its cultural evolution, became the “owner” of the planet, with negative and probable fatal consequences, to its own species and many other life forms. In this article, I sketch the guidelines to come back to our symbiotic horizon, with the aplication of bioethical principles of justice and benefit , to think of a better future to human race and our planet, Earth.