Ancient Worms May have saved Earth.

So how exactly did the earth maintain the perfect balance of oxygen to allow life on earth to flourish?

Well, the idea is that as they dug and wiggled these early multicellular creatures.  Exposed new layers of seafloor sediment to the ocean's water. Each new batch of sediment that settles on to the seafloor contains bacteria. As those bacteria were exposed to the oxygen in the water, they began storing a chemical called phosphate in their cells. So as the creatures churned up more sediment layers, more phosphate built up in Ocean sediments and less was found in seawater.

Because algae and other photosynthesis ocean life require phosphate to grow, removing phosphate from seawater reduced their growth. Fewer phosphors thesis, in turn, meant less oxygen released into the ocean. In this way, the system formed a negative feedback loop automatically slowed the rise in oxygen levels as the levels increased.

Less oxygen in the water also meant fewer worms, so less oxygen-rescuing digging, thus these animals may have completely transformed the geochemical cycle.

Too little oxygen and nascent animals would have suffocated. Too much and lightings strikes would have created catastrophic fires, torching the primordial land vegetation thus hindering life on Earth. But a new study shows that a primordial worm may have spread us from this fate 500 million years ago by maintaining the balance of oxygen.