It’s the move to eukaryotic life, or “complex cells” that’s unique. Multicellularity given eukaryotic status seems easy, but eukaryote status happened only once, and about halfway through the habitable lifetime of the Earth.
Life on Earth arose very early in its history so if life arising is the hard and rare step I would expect there to be many more hundreds of millions or even billions of years of conditions on Earth being seemingly ripe for it arising and it not doing so.
This argument is faulty if there is more than one hard step (and the update is not that strong, although significant, even with one step). See Robin’s paper for details.
It’s the move to eukaryotic life, or “complex cells” that’s unique. Multicellularity given eukaryotic status seems easy, but eukaryote status happened only once, and about halfway through the habitable lifetime of the Earth.
Thank you for correcting me on this, it has been some time since I thought of this.
This argument is faulty if there is more than one hard step (and the update is not that strong, although significant, even with one step). See Robin’s paper for details.