Timeline of Photosynthesis on Earth

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Editors note: This story is part of a Feature "The Color of Plants on Other Worlds" from the April 2008 issue of Scientific American.

Photosynthesis evolved early in Earth’s history. The rapidity of its emergence suggests it was no fluke and could arise on other worlds, too. As organisms released gases that changed the very lighting conditions on which they depended, they had to evolve new colors.

4.6 billion years ago -- Formation of Earth

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3.4 billion years ago -- First photosynthetic bacteria
They absorbed near-infrared rather than visible light and produced sulfur or sulfate compounds rather than oxygen. Their pigments (possibly bacteriochlorophylls) were predecessors to chlorophyll.

2.4–2.3 billion years ago -- First rock evidence of atmospheric oxygen

2.7 billion years ago -- Cyanobacteria
These ubiquitous bacteria were the first oxygen producers. They absorb visible light using a mix of pigments: phycobilins, carotenoids and several forms of chlorophyll.

1.2billion years ago -- Red and brown algae
These organisms have more complex cellular structures than bacteria do. Like cyanobacteria, they contain phycobilin pigments as well as various forms of chlorophyll.

0.75billion years ago -- Green algae
Green algae do better than red and brown algae in the strong light of shallow water. They make do without phycobilins.

0.475billion years ago -- First land plants
Mosses and liverworts descended from green algae. Lacking vascular structure (stems and roots) to pull water from the soil, they are unable to grow tall.

0.423 billion years ago -- Vascular plants
These are literally garden-variety plants, such as ferns, grasses, trees and cacti. They are able to grow tall canopies to capture more light.

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