It is simple to understand why photosynthesis was necessary to evolve and why it was favorable to both plants and other organisms that used sunlight to generate its own food source; water is abundant so using it as an electron source was ideal, as well as the created ozone layer that was produced from photosynthetic activity for protection from ultraviolet radiation of the sun. Why the evolution of photosynthesis occurred and persisted (as well as other evolutionary processes) is a simple answer: because it works. However, determining when photosynthesis arose is a fundamental question because we can then understand why it arose specifically at this time and the changes it implemented on the other life forms it impacted.
It was interesting that many base the origin of photosynthesis around the great oxidation event (GOE), which marks signs of when atmospheric oxygen is sustained, and assume that photosynthesis arises shortly after levels of oxygen are available. I found myself agreeing with the scientists that believed in theories that photosynthetic-like activity originated years before the GOE, because although the abundance of atmospheric oxygen was apparent, the rise of oxygen must have been a result of photosynthetic activity expelling oxygen as a waste product coupled with carbon dioxide intake. Out of all the early-origin for photosynthesis cases, I thought that the evolution of incorporating RuBisCo, was most fascinating; although RuBisCo evolved prior to the abundance of atmospheric oxygen, RuBisCo binds to both oxygen and carbon dioxide, but the affinity for carbon dioxide is much higher. Since both substrates competitively inhibit eachother, photosynthesis begins when carbon dioxide is available, but photorespiration with an end product of carbon dioxide will result if RuBisCo can only bind to oxygen. I saw this arrangement as unbelievably perfect knowing that the highly conserved RuBisCo was already formed long before the origination of photosynthesis.
This article was particularly significant to me because a large part of the early photosynthesis evidence was observing effects of the atmospheric and environmental conditions to the microbes during this time. My thesis project surrounds the potential effects of a nanomaterial to the bacterial community if it was released to the natural world, and I believe microorganisms are investigated because microbial systems are the first to be affected in any change to the environment. Thus, the origins of photosynthesis can be observed through the bacterial communities, such as the 3.2 billion year old shale deposits in Australia containing bacteria that used water as electron deposits, because any slight change to the natural world will affect the microbial systems.