He’s also not paying attention to the fact that most photosynthesis on earth is a.) not done by plants, b.) not done on land, and c.) not done by eukaryotes at all. As I’m sure you’re aware, the massive size of eukaryotic cells, the segmentation of transcription and translation, and the complexity imposed by all those membrane-bound organelles means that plants have to expend a good deal of energy just on shuttling things about; if you’ve ever seen the chloroplasts running around inside a plant cell, it gives a feel for the energy expendiatures that eukaryotes spend on non-fixation activities.

By contrast, a prokaryote like Nostoc (closely related to Anabaena, but freshwater, and the current target of my research) is something like a free-living chloroplast – in fact, it’s been shown that chloroplasts evolved from them. Their primary structural feature is stacked thylakoid membranes underneath the cell wall. They rely on their boyancy from their mucilage sheath to keep them close to sunlight.

This is why, when conditions are right, a bloom of cyanobacteria can absorb – and fix – almost 80% of the incoming solar energy that impinges upon the surface of water. It is the combination of radical increase in efficiency, incredibly rapid growth rate (doubling every hour or so under optimal conditions), and lack of energy expendiature on just about anything other than fixation either into sugars or lipids that lead me to think that Mr Diamond’s contention is incorrect.