Re: whats the temporal order of aerobic, anaerobic respiration & photosynthesis

Dear questionner,

Thanks for your interesting question. First, let me point you to my previous answer on MadSci: Is chemosynthesis older than photosynthesis?, which covers similar ground to your question.

We can figure out the order of anaerobic/aerobic respiration and photosynthesis by examining geological evidence and using a bit of logic, in the following way:

• The only major source of oxygen on earth is generated when photosynthetic organisms split water. So aerobic respiration, which uses oxygen, must have evolved later than photosynthesis.
• The first evidence for oxygen in the atmosphere is 2.3 billion years old. The first evidence for cells is about 3.6 billion years old. So the first cells must have utilised anaerobic respiration.
• Therefore, the temporal order is: anaerobic respiration first, then photosynthesis, then aerobic respiration.

Here are some links that illustrate the evidence for cellular evolution:

• A survey of the fossil record
  A very informative page. Scroll down to see images of the earliest-known cells in rocks that are 3.5 billion years old.
• Evolution of the atmosphere and the rise of oxygen
  These lecture notes from a Washington University course describe the appearance of oxygen in the atmosphere; includes pictures of "banded iron", the geological evidence.
• From Soup to Cells - the Origin of Life
  Information and links from a Berkeley University course.
• Wikipedia Origin of Life category
  May have some useful links to more information.
• The Astrobiology Web and Astrobiology Magazine have many articles on the origin and evolution of cells.
• The TalkOrigins Archive
  Main focus is the creationism/evolution debate, but contains some good articles on cellular evolution.