About 2.5 billion years ago, though consensus on that date hasn’t yet been reached, one of the greatest calamities to knock life on Earth occurred. That event would have profound implications on the development of life from then on. Ultimately, it allowed complicated life to arise on earth, and after more mass extinctions, eventually led to us. This great planetary calamity came from an unlikely source. Indeed it is today one of the hallmarks of the earth’s atmosphere, and we die very quickly without it. It was oxygen. However, oxygen as we know and breathe it, O2, was not always present in the earth’s atmosphere in high concentration and while we all know the reason it’s there, photosynthesis by plants, it was also deadly poisonous to some of the earth’s earliest life.
Evolution Of Multicellular Organisms.
Sometime before 2.3 billion years ago multicellular organisms evolved called Cyanobacteria or what used to be called Blue-Green algae though that term is out of date. These aquatic organisms were the first life on planet earth to be capable of photosynthesis. The byproduct of photosynthesis is, of course, oxygen. Initially, this was not an issue. Oxygen is reactive and likes to bond with other elements. It would do so with features such as iron early in the Earth’s history, and that would keep it safely locked up. At some point, however, the planet’s oxygen sinks became saturated which allowed a build-up of oxygen in the ocean and atmosphere. This was toxic to the anaerobic bacteria living in the sea, and they began to die off.
Earth was warm during this period of history because of methane, which is an active greenhouse gas. Trouble is when you start involving oxygen with methane, they react, and one of the products of that is carbon dioxide. That interaction increased the levels of CO2 in the earth’s atmosphere. Now, we tend to think of carbon dioxide as a greenhouse gas in and of itself, especially in the context of human production of it and the atmospheric effects of that. Moreover, it is a greenhouse gas, but it’s nowhere near as efficient as methane when trapping heat
The Huronian glaciation was a time when increased atmospheric oxygen decreased atmospheric methane. The oxygen combined with the methane to form carbon dioxide and water, which do not retain heatRevolvy
as well as methanedoes.
This seemingly life-caused mass extinction isn’t the only one. Fast forward to the dawn of humankind. We are linked to thousands of extinctions from amphibians to megafauna. One could argue that these extinctions are due to the advent of technology, but at its most basic level, we have merely changed the conditions of the planet like our cyanobacteria forbearers did. Perhaps someday we can bring those species back through a mastery of genetics and halt the Great Holocene extinction event. However, it makes me wonder how often things like the excellent oxygenation event happen to habitable planets in the universe. Does life often develop on other worlds only to routinely destroy itself at the microbial level? Are there worlds where oxygen creation have never happened for some reason? Might these anaerobic worlds harbor complicated anaerobic life? We have seen such things on our planet, albeit rarely and it’s hard to envision anaerobic organisms ever getting too complicated. However, it’s well worth wondering about.
Get your daily education, entertainment, science & technology, sports and travel tips from Johnny, TODAY! It's absolutely FREE and always will be.