540 million years ago, ancient poop caused life to explode on Earth

Nearly 540 million years ago, the Cambrian explosion happened when life exploded and expanded dramatically. Scientists now have a cause for it - poop. A study published in Trends in Ecology & Evolution states that as faecal matter slowly accumulated, it distributed organic material and nutrients throughout the ocean. This created the right conditions for life to be born and evolve. The study notes that fossilised faeces and the emergence of animals with complex digestive systems are linked.

Study co-author Russell Bicknell said that the importance of faeces in ancient ecosystems is often overlooked, with oxygen levels being given more importance. Turns out, poop played a major role in the evolutionary explosion during the Cambrian period. It took place around 539 million to 485 million years ago. Almost all major animal groups we know of on Earth today emerged during this time. Scientists treat this time period as a benchmark for the evolution of early life on Earth.

Complex digestive systems emerged because of poop

Fossilised faeces, also called coprolites, are from the time around the onset of the Cambrian, co-author Julien Kimming, a palaeontologist at the Karlsruhe Institute of Technology in Germany, and Bicknell wrote in The Conversation. There is also no evidence of complex digestive systems before the Cambrian. "As we move forwards in time, more diverse coprolites appear. Associated with this shift, there was an increase in very well-preserved fossils with complex digestive systems, particularly among early arthropods," they wrote.

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The researchers state in the study that until now, all studies have focused on oxygen levels, food webs, or biogeochemical cycles during the Cambrian. The authors started off with the aim to explore the origin and role of faecal matter, as today poop is a vital element of the marine biological pump. They talk about an ecological feedback loop in which more poop added more nutrients into the environment, thus supporting more animals and consequently leading to more poop.

The scientists say this isn't any different from other theories about life on Earth. In most systems on Earth, a combination of various elements triggered a feedback loop, leading to something bigger to be born. In the case of the Cambrian, poop played a vital role in triggering life to be born, as did other elements.