The transition between single-celled life and multicellular life is one of the most important evolutionary “level-ups” to occur in the game of life (then again, being a multicellular organism, I would obviously say that). As documented in a remarkable new study, you can now watch this transition unfold before your eyes.
Biologists at the University of Montana and the Georgia Institute of Technology witnessed single-celled algae evolve into a multicellular organism in response to the threat of a predator within a period of just 50 weeks. Thankfully, you don’t have to wait that long, you can watch it in this short time-lapse video below.
This transition from unicellular to complex multicellular life has occurred dozens of separate times throughout the history of life on Earth – animals, land plants, fungi, red algae, brown algae, and several groups of green algae all have separate unicellular ancestors. However, scientists have always quarreled about why these change might have arisen. The new research adds to the body of evidence that suggests the threat of predators might have been one of the many culprits, just as some researchers have previously pondered.
Reporting in the journal Scientific Reports, the team of scientists wanted to see how multicellularity can evolve in response to predation. They placed populations of the single-celled green alga, Chlamydomonas reinhardtii, alongside a single-celled predator, Paramecium tetraurelia, and watched the drama unfold.
By week 50, around 750 generations, the shift to multicellular structures was notable. The green algae had banded together and formed clusters made up of multiple cells, creating a structure that was too big to be consumed by the predators.
"Survival assays show that evolved multicellular traits provide effective protection against predation,” the study authors write.
The authors note some origins of multicellularity, such as brown algae, occurred after the rise of animals and were potentially driven by animal predation. They also remark that the whole process appears to be remarkably easy, much like how other scientists have explained the phenomenon.
Perhaps, the journey from unicellular life to multicellular life is not the momentous leap it is often imagined to be.
“Observations in other species suggest that the relative ease of transitioning from a unicellular to a multicellular life cycle is at least somewhat general. Similar transitions reportedly occurred within 100 generations in the green alga Chlorella vulgaris and within 300 generations in the yeast Saccharomyces cerevisiae,” the researchers wrote.