"The transition to multicellular organisms with many kinds of differentiated cells occurred on three occasions, suggesting that it may not have been particuularly difficult. This would be explained if the main cellular novelty required was an epigenetic inheritance system, as this existed already in protists. If so, the emergence and radiation of the metazoa had to wait only for suitable environmental condition."
p.231 of Szathmary, E. and J. Maynard-Smith. 1995. The Major Evolutionary Transitions. Nature 374:227-232.
Well, maybe. There's a lot going on in that sentence
I wonder what evolutionary transitions -- I mean really big ones, like the origin of molecular coding or sexual replication -- are or can still occur in Earth life-forms?
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