A new clue to how multicellular life may have evolved

The idea for the work came from watching the filter feeding of stentors — trumpet-shaped, single-celled giants that float near the surface of ponds. (Getty Images)

Life emerged on Earth some 3.8 billion years ago. The “primordial soup theory” proposes that chemicals floating in pools of water, in the presence of sunlight and electrical discharge, spontaneously formed organic molecules. These building blocks of life underwent chemical reactions, likely driven by RNA, eventually leading to the formation of single cells. 

But what sparked single cells to assemble into more complex, multicellular life forms? 

Nature Physics published a new insight about a possible driver of this key step in evolution — the fluid dynamics of cooperative feeding. 

“So much work on the origins of multicellular life focuses on chemistry,” says Shashank Shekhar, lead author of the study and assistant professor of physics at Emory University. “We wanted to investigate the role of physical forces in the process.” 

Shekhar got the idea while watching the filter feeding of stentors — trumpet-shaped, single-celled giants that float near the surface of ponds. Through microscope video, he captured the fluid dynamics of a stentor in a liquid-filled lab dish as the organism sucked in particles suspended in the liquid. He also recorded the fluid dynamics of pairs and groups of stentors clumped together and feeding. 

The videos revealed a world similar to how Van Gogh saw the night sky, swirling with stars. 

“The project started with beautiful images of the fluid flows,” Shekhar says. “Only later did we realize the evolutionary significance of this behavior.”

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