New Understanding of the Evolution of Multicellular Life

In 2017, researchers discovered Chromosphaera perkinsii, a single-celled organism, in marine sediments in Hawaii. According to scientists from the University of Geneva, this organism can form multicellular structures resembling early animal embryos, providing insight into the origins of multicellularity. This species, which diverged from the animal evolutionary line over a billion years ago, suggests that key processes underlying multicellular development may have existed well before animals appeared on Earth.

These findings imply one of two possibilities: either C. perkinsii evolved similar processes independently, or the genetic pathways controlling embryonic development predate animal life. In essence, nature may have had the genetic “blueprints” for creating complex multicellular organisms long before animals, including those that lay eggs, emerged. This study, published in Nature, sheds light on the evolutionary precursors to multicellularity.

The earliest life forms on Earth were unicellular, consisting of single cells like bacteria or yeast. Animals, however, evolved from single egg cells into multicellular organisms, a process involving coordinated cellular differentiation and growth. Yet, how unicellular organisms transitioned to multicellularity has remained largely unknown.

Omaya Dudin, an Assistant Professor in Biochemistry at the University of Geneva and the study lead, has been investigating the ancestral protist C. perkinsii. His team observed that when these cells reach a maximum size, they divide without further growth, forming multicellular colonies similar to early animal embryos. Remarkably, these colonies contain at least two distinct cell types and persist for about a third of their life cycle, displaying early multicellular coordination and differentiation well before animals appeared.

In collaboration with Dr. John Burns of the Bigelow Laboratory for Ocean Sciences, the team analyzed genetic activity in these colonies, finding surprising parallels with animal embryos. This suggests that the genetic programs enabling multicellular development may have been in place more than a billion years ago.

The study’s first author, Marine Olivetta, a lab technician at the University of Geneva, noted the significance of this discovery: “It’s fascinating that a species discovered so recently allows us to look back in time more than a billion years.”

These findings challenge conventional assumptions about the origins of multicellularity and could shed new light on long-debated 600-million-year-old fossils resembling embryos. They suggest that either embryonic development pathways existed before animals or multicellular mechanisms evolved independently in C. perkinsii, prompting a fresh look at the evolution of life’s complexity.