Did poop enable the evolution of complex animals?

The Cambrian explosion, which occurred approximately 540 million years ago, represents a pivotal era of rapid evolutionary expansion on Earth that established most modern animal lineages.

A new scientific study suggests this major biological milestone may have been driven by a seemingly simple evolutionary development: the emergence of digestive tracts and the resulting fecal waste. By examining ancient fossilized digestive systems alongside fossilized excrement from around the globe, researchers reconstructed how early biological waste significantly altered the chemical composition of the ancient oceans, facilitating the transition from simple life forms to complex marine ecosystems.\n\nAccording to the research, the introduction of fecal pellets functioned as a primitive biological pump, carrying vital nutrients like carbon, nitrogen, iron, and phosphorus down to previously barren depths of the sea. Before this development, primitive organisms like sponges lacked internal digestive organs and merely absorbed food particles directly from shallow water, leaving the deeper waters largely uninhabitable due to a lack of resources. The downward drift of organic waste deposited essential resources into these deep layers, triggering a positive feedback loop where larger, more complex organisms could thrive, produce even larger waste deposits, and ultimately support the highly diverse marine food webs we see today.