The first land plants may have triggered a rush of animal evolution, according to a controversial theory proposed by German researchers.
Land plants increased erosion, argue Werner von Bloh and colleagues, of the Potsdam Institute for Climate Impact Research, in Geophysical Research Letters.
Calcium in the newly exposed minerals reacted with carbon dioxide in the air to make calcium carbonate, or limestone. Rivers washed this to the sea, sealing the carbon in the ocean bed. The loss of carbon dioxide weakened the greenhouse effect and cooled the Earth.
Once the temperature fell below a certain threshold, a runaway process began, says the team.
When conditions became favourable for complex life, these organisms cooled the Earth yet further, and so on.
Many researchers, however, think that rising, not falling, temperatures lit the fuse for the Cambrian explosion, the biological Big Bang 540m years ago when most modern animal groups appear in the fossil record.
