It is often asserted that our planet presents the optimal conditions to sustain life, yet this assessment overlooks the fact that these characteristics are the result of the actions of living organisms over approximately four billion years. Biodiversity, in its richness of forms and relationships, is the sole guarantee for maintaining these parameters within a regime of acceptable fluctuations and timescales of change. Life on Earth has also experienced catastrophic events that caused mass extinctions and radical transformations in living forms. These mass extinctions were usually triggered by external factors, such as asteroid impacts or increased volcanic activity; today, however, humanity is the cause of a new mass extinction.