I recently read a review article in 4/30 Science about photosynthesis—not being a biologist I didn’t realize
there was more than one kind - “C3” (high school biology), C4, and CAM
http://en.wikipedia.org/wiki/C4_carbon_fixation
C4 was only discovered in 1966…

In this link {
http://www.palaeobiology.org.uk/projects_05.htm}  the evolution of C4 is discussed—they note that

Less than 4% of plant species use the C4 pathway, but on a global scale they annually account for 20% of plant growth (net primary production). Yet this tremendous worldwide significance has been reached in a short stretch of geological time, with the evolution of C4 species from C3 predecessors occurring only within the last 25 Million years or so.

The Wikipedia article notes that that the C4 plants became ecologically significant only 6-7 million years ago, and mentions them in regard to climate change amelioration (because the grasses sequester CO2).

Apparently C4 evolved in response to lower levels of CO2 in the atmosphere, and is more efficient under certain conditions. C4 plants include grasses mainly (as far as I can see) including corn and sugar cane.

Interesting Jackson, thanks. I had no idea.

Ditto here!

The evolution of flowering plants is pretty well known (well I know about it) and for
example Dawkins mentions it in Greatest Show on Earth as do others.

But either I had just skipped over it or never picked up the right book.

Some scientists seem to think that C4 is as important an evolutionary development in its own way.

Jackson - 13 June 2010 04:05 AM

I recently read a review article in 4/30 Science about photosynthesis—not being a biologist I didn’t realize
there was more than one kind - “C3” (high school biology), C4, and CAM
http://en.wikipedia.org/wiki/C4_carbon_fixation
C4 was only discovered in 1966…

In this link {
http://www.palaeobiology.org.uk/projects_05.htm}  the evolution of C4 is discussed—they note that

Less than 4% of plant species use the C4 pathway, but on a global scale they annually account for 20% of plant growth (net primary production). Yet this tremendous worldwide significance has been reached in a short stretch of geological time, with the evolution of C4 species from C3 predecessors occurring only within the last 25 Million years or so.

The Wikipedia article notes that that the C4 plants became ecologically significant only 6-7 million years ago, and mentions them in regard to climate change amelioration (because the grasses sequester CO2).

Apparently C4 evolved in response to lower levels of CO2 in the atmosphere, and is more efficient under certain conditions. C4 plants include grasses mainly (as far as I can see) including corn and sugar cane.

If those C4 plants include corn and sugar cane, how much of this increase is due to farming?