The Cambrian Explosion was long considered to be the origin of multicellular animal life. The discovery of Ediacaran crawling and sessile animal fossils which emerged during the Avalon Explosion debunked this idea. So, chances are we are mistaken again, and complex animal life arose before the Ediacaran. A gradual emergence of multicellularity is also more likely than a spontaneous explosion of highly complex animals.

There is some evidence to suggest that sponge-like animals appeared 890 million to a billion years ago, supplying early pieces to the puzzle that is the transition from single- to multicellular animal life. The rise of multicellularity directly follows the emergence of eukaryotes and therefore must be closely linked to the evolution of sex. Some of the oldest animals were even fossilized while mating in large groups. So, a better appreciation and understanding of the diversity of sex in the sea will likely shed light on multicellularity.

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