Single-Celled Ancestors of Animals Were Prepared for the Evolutionary Leap

Study finds single-celled organisms regulate their cellular processes with many of the same tools as multicellular animals.

Roughly 800 million years ago, the first multicellular animals evolved from single-celled organisms. New research published in Developmental Cell suggests these single-celled ancestors were well-equipped for the major transition, with mechanisms already in place to allow different tissue types to develop.

"We're looking into the past at an evolutionary transition that was important for the origin of all animals," explains study co-author Iñaki Ruiz-Trillo, an evolutionary biologist at the Institute of Evolutionary Biology in Barcelona, Spain, in a press release.

LEARN MORE: Brainless Slime Shows Signs of Intelligence, Scientists Find

"We show that these early organisms already had some behaviors that we once thought were only in multicellular animals. From there, it would have been a simpler evolutionary leap," he says.

The single-celled amoeba, Capsaspora owczarzaki, is a close relative of modern-day multi-cellular animals. But this particular species is interesting because lone amoebas will aggregate together at a certain point in their life cycle.

A team of researchers wanted to know how these amoebas were regulating their internal cell processes during the solitary phase, and during the aggregated phase.

Focusing on protein expression and modification within the cells, the researchers discovered that the single-celled amoebas were using “the same mechanisms that animals use to differentiate one cell type from another,” but which hadn’t previously been observed in single-celled organisms, according to Ruiz-Trillo.

One example was a tyrosine-kinase signalling system, which the amoebas activated to regulate protein formation. The researchers concluded that this tool, which is also present in animals, was most likely inherited from their single-celled ancestors.

"The ancestor already had the tools that the cell needed to differentiate into different tissues," says study co-author Eduard Sabidó of the Proteomics Unit of the Centre for Genomic Regulation in Spain. "The cells that were around before animals were more or less prepared for this leap."

You might also like: Rare Brain-Eating Amoeba Infects and Kills 18-Year-Old Ohio Teen