Marine planktonic diatoms are responsible for up to 20% of primary production on earth, fixing more than 10 billion tons of inorganic carbon each year. The existence of both the C3 and C4 pathways were recently discovered in a marine diatom. In this unicellular organism, the two paths are kept separate by having the C4 path in the cytosol, and the C3 path confined to the chloroplast. What are the evolutionary implications of this discovery?