Study suggests animal feces fueled Cambrian Explosion by distributing ocean nutrients

The Cambrian Explosion and Early Animal Evolution

Around 600 million years ago, the first animals appeared on Earth. Approximately 60 million years later, these simple organisms underwent a period of rapid diversification known as the Cambrian Explosion. This evolutionary burst led to the emergence of most animal phyla and complex ecosystems observed today.

The Role of Feces in Nutrient Distribution

A study by Julien Kimming of Karlsruhe Institute of Technology and Russell Bicknell of Flinders University suggests that the evolution of animal digestive systems and the subsequent production of fecal pellets were key to this diversification. They propose that these early feces helped spread vital nutrients to the deeper parts of the ocean.

Investigating Ancient Digestive Systems and Coprolites

Kimming and Bicknell analyzed scientific literature for fossilized digestive systems and Cambrian-period coprolites (fossilized fecal matter) to track their evolution. They also compared modern ocean nutrient cycles with simulated and geological evidence of ocean chemistry from 540 million years ago. Their findings indicate that raw nutrients, crucial for the ancestors of modern animal phyla, reached ocean depths via feces.

Feces and the Ocean's Biological Pump

Today, animal feces are integral to the ocean's biological pump, which circulates nutrients like carbon, iron, nitrogen, and phosphorus. Before about 540 million years ago, during the Ediacaran Period, deeper ocean regions were less habitable. Kimming and Bicknell argue that the advent of fecal pellets provided an additional source of organic carbon and other nutrients to deeper waters, significantly boosting support for marine animal life and facilitating diversification.