Final answer:
Diverse multicellular eukaryotes didn't appear until the Ediacaran period, around 600 to 700 million years ago.
Step-by-step explanation:
The appearance of diverse multicellular eukaryotes didn't occur until the Ediacaran period, which was around 600 to 700 million years ago. The Ediacaran period marked the appearance of flat and soft-bodied multicellular creatures called Ediacarans. These organisms were the early ancestors of the multicellular eukaryotes that exist today.