New research is redefining our understanding of the history of life on the planet, suggesting that a common biological function may have been crucial to the development of complex forms. In a recent study published on August 12, 2026, scientists point out that the ability to defecate, developed by primitive animals, drove the rapid diversification of species known as the Cambrian Explosion.
This discovery adds an unexpected layer to the already intricate tapestry of evolution. It highlights how seemingly simple biological processes can have monumental impacts on ecosystems and the emergence of all the complex life we see in the oceans and on Earth today.
Understanding the Cambrian Explosion and the new hypothesis about feces
Approximately 600 million years ago, the first animals appeared on Earth, predominantly simple and with basic structures. Sixty million years later, a period of intense evolutionary change occurred, where these primitive creatures transformed into a vast array of new complex forms, carving out diverse ecological niches. This event, known as the Cambrian Explosion, generated most of the groups of animals and marine ecosystems present today.
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An innovative hypothesis proposes that this evolutionary leap may have been fueled by the development of a fundamental biological ability: defecation. The first animal excrement would have been essential for the distribution of nutrients in the ocean depths, catalyzing the evolution of larger beings and more complex ecosystems.
Research reveals unprecedented role of marine organic waste
Paleontologist Julien Kimming, from the Karlsruhe Institute of Technology, and paleobiologist Russell Bicknell, from Flinders University, led the study that investigated the origin of this theory. They exhaustively analyzed the scientific literature, searching for records of fossilized digestive systems and coprolites (fossilized fecal matter) from the Cambrian period. This made it possible to map the evolution of digestive tracts and excrement over geological time.
The research also included an in-depth comparison between the nutrient cycles that support life in the modern oceans and the estimated chemical composition of the oceans 540 million years ago, based on simulations and geological evidence. This detailed analysis revealed that nutrients vital to the ancestors of today’s animal phyla likely reached the depths of the ocean thanks to the action of feces.
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The oceans’ biological pump and support for deep life
In today’s oceans, the water is abundantly filled with excrement from a wide range of sea creatures, from tiny zooplankton to giants like blue whales. These organic wastes form a vital component of a system known as the “biological pump.” This pump works to transport essential nutrients, such as carbon, iron, nitrogen and phosphorus, to the deepest layers of the ocean, away from the sunlit surface.
Without the efficiency of this biological pump, the ocean depths would be considerably less conducive to life than they are today. This condition of scarcity was quite common until the end of the Ediacaran period, around 540 million years ago. Kimming and Bicknell argue that as animals developed the first digestive systems, they began sending the first excrement to the sea floor, providing a crucial initial boost to this primitive biological pump. The arrival of this organic waste would have transformed previously inhospitable environments, making them capable of supporting new forms of life.
The researchers highlight the relevance of this debris. “The emergence of fecal pellets,” wrote Kimming and Bicknell, “provided an additional source of organic carbon, as well as iron, nitrogen, and phosphorus, to deeper waters. In this context, fecal pellets significantly increased support for marine animal life and possibly contributed to diversification and increased biomass in the Cambrian period.”
Radical transformation: from simple life to complex ecosystems
The first animals on Earth were predominantly simple creatures, inhabiting the surface layers of the ocean, where sunlight penetrated, or the shallow areas of the seabed. These organisms, often compared to sponges or jellyfish, did not have complex internal organs. Their diet consisted of waiting for tiny particles, such as plankton or bacteria, to float to the openings of their bodies, which were then absorbed and processed cellularly.
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What these animals released back into the ocean were mainly chemical byproducts of their cellular metabolism, with low nutritional value for other organisms. Consequently, the ocean depths remained largely uninhabited, as they did not offer sufficient nutrients to maintain animal life. The evolution of digestive systems and, by extension, feces, drastically changed this scenario.
Around 580 million years ago, some animals began to develop rudimentary organs, including primitive intestines. This meant a revolution: they could swallow larger pieces of food and digest them outside the cells, a much more efficient method. This new capacity allowed animals to feed more frequently, supporting more complex bodies. At the same time, it required the elimination of undigested or absorbed parts, marking the emergence of excrement as we know it today.
Coprolite discoveries: fossil traces of evolution
To date, paleontologists have found coprolites from the Cambrian period in about 35 archaeological sites around the world. These finds cover a period stretching from approximately 540 to 494 million years ago, providing concrete evidence of the role of excrement in ancient life.
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- Fecal fossils show a remarkable variety, with diverse characteristics:
- Size:They range from microscopic structures to several centimeters in length.
- Shapes:They include elongated, cylindrical, ellipsoid, circular and even “exploded” shapes, as Kimming and Bicknell described.
- Content:Some of the larger coprolites contain fragments of shells or exoskeletons, offering valuable clues about the diet of the animals that produced them.
The great diversity in size and shape of these fossilized coprolites suggests that the animals responsible for them were also incredibly diverse. However, the scientific community is still working to match many of the Cambrian fossil animals to corresponding coprolites, a challenge that continues to instigate new research. The ability to analyze these organic residues gives us a unique window into understanding the habits and complexity of ancient ecosystems.