Cilia - Tails of the unexpected

When Chlamydomonas mates meet, their flagella intertwine, sticking together and triggering a cascade of chemical signals that directs the cells to fuse. This signaling, cooperation and clustering is reminiscent of a momentous biological step. 'It's a flirtation with multicellularity as far as I'm concerned,' says Bill Snell, a cell biologist and expert on chlamy at the University of Texas Southwestern Medical School in Dallas. About 700 million years ago, single cells clubbed together perhaps using flagella and other similar structures to cooperate and communicate, forming the first multicellular organisms. Biologists are realizing that signs of this unicellular ancestry are etched on almost every single cell of our bodies in the form of cilia, shortened versions of flagella that our unicellular ancestors used to flit through Precambrian seas.