Scientists: Animals' Digestive Tract May Have Been Triggered by Dense Cellular Cooperation

A new theory proposes that the evolutionary foundation of animals' digestive systems was laid when single-celled organisms began working together in tight cooperation. All animals, from mosquitoes to elephants, consist of many cells, except for protozoans such as amoebas. Scientists believe this cellular merger occurred in the distant past.

A new scientific theory offers an intriguing explanation for how animals' digestive systems could have emerged during evolution. Specifically, it is believed that single-celled organisms merged with one another in the distant past so tightly that they began to function as a single integrated organism, and this tight assembly may have laid the foundation for all animals' digestive systems.

All known animals, from tiny mosquitoes to giant elephants, consist of numerous cells. The exception is protozoans, such as amoebas and rotifers, which scientists do not actually consider true animals. These are single-celled living organisms that live independently and do not form more complex communities.

According to the theory, the transformation took place in antiquity: single-celled organisms, which previously lived separately, began to function in coordinated cooperation. This process, in which cells shared different functions and were in constant close contact with one another, created the foundation for more complex body organisation, including the digestive system that enables digestion.

Such an evolutionary leap is one of biology's fundamental questions: how did multicellularity arise, and what advantages did it offer early life? Contemporary research on the behaviour of single-celled organisms helps scientists better understand and reconstruct this ancient transition.