Even after single-celled organisms had been around for a couple billion years, they did not transition to being multicellular.
Paul worded the question “what took so long?“.
A multitude of transitions to multicellularity happened independently in different lineages, in different times.
Multicellularity evolved in different time periods and different lineages; for example, cyanobacteria were evolving multicellularity with honest-to-goodness development around 3 billion years ago.
The evolution of multicellularity is broader than just animals; it’s a process through which lineages that are single-celled form groups that become evolutionary units that can get more complex through natural selection.
There’s a huge knowledge gap in evolutionary biology around how simple groups become complex, which is why Will Ratcliff has been studying snowflake yeast to see how they become more complex.
The transition to individuals that become organisms is universal across lineages, and we’ve never seen those processes play out in nature.
One of the beautiful things about working with yeast is that you can also throw synthetic biology into that pot.
