From one cell to many: How did multicellularity evolve?
Geege Schuman stashed this in Science Too
Interestingly, this “alignment-of-fitness” requires a “bottleneck” or unicellular stage when the organism consists of just one cell—a spore, zygote, or uninucleate asexual propagule. This is necessary so that all subsequent cells share similar genetic material.
The “export-of-fitness” stage is the second step necessary to the evolutionary process of multicellularity. This requires that cells work together for a common goal of reproducing more cohesive units, or individuals, like themselves and thereby work in a concerted way toward increasing their fitness. Once this is achieved, a distinct phenotype, or form, of organism exists.
How exactly steps such as cell-to-cell adhesion or communication were achieved in plants, animals, fungi, and algae differs among the major eukaryotic clades, yet an important aspect is that these multicellular organisms all went through a similar series of steps on their way to becoming multicellular, functional organisms.
As Niklas puts it: “This convergent evolution is well summarized by the saying ‘There are many roads to Rome, but Rome is not what it used to be’.”
(Sounds like a business model!)
It really does seem like the hardest work is going from 1 cell to 2 cells.
Going from 2 cells to multicells seems like a straightforward running of the process.
But going from 1 to 2 is a giant leap.