MULTICELLULARITY ROLE. “Our results indicate an origin of cyanobacteria before the rise of atmospheric oxygen. The evolution of multicellular forms coincides with the onset of the GOE and an increase in diversification rates. These results suggest that multicellularity could have played a key role in triggering cyanobacterial evolution around the GOE.” (GOE = Great Oxygenation Event).
http://www.pnas.org/content/110/5/1791.full