Go for Gaia
In the 1970s James Lovelock developed the idea that Earth can be seen as a giant self-regulating organism – the Gaia hypothesis
Lovelock’s theory was that Earth was optimised to maintain life. Although widely dismissed by mainstream science at the time, modified versions of the hypothesis have emerged as an influential factor in climate debates. The idea that biological, geological and atmospheric systems interact at a global level, in ways that sustain life on Earth, is now widely appreciated (though still somewhat contentious).
Gaia helps to explain why the salinity of the oceans remains constant, and therefore supports life, despite the fact that rivers are constantly dissolving salt from rocks and carrying it to the ocean. This explanation lies in the cracks in the ocean floor: as the seawater passes through these cracks, the salt is removed, and the overall salinity remains constant.
Now, human activities are in danger of altering these systems so profoundly that they may struggle to support human life in the future.