The 1.2-billion-year-old Hunting Formation on Somerset Island, Canada, dates from the end of the Ectasian.

It contains the microfossils of the multicellular filaments of Bangiomorpha pubescens (type of red algae), the first taxonomically resolved eukaryote.

This was the first organism that exhibited sexual reproduction, which is an essential feature for complex multicellularity.

This is, in fact, an essential feature of sexual reproduction as well, since the male and female gametes are specialized cells.

Sexual reproduction and the ability of gametes to develop into an organism are the necessary antecedents to true multicellularity.