Before starting the second part, i would like to apologize for the delay. I was not super busy or anything, just being plain lazy without any excuses.
Moving on, When did life actually started? No one can actually tell. However scientists believe that life could have started or originated on multiple occasion and scenarios, only to be denied by major impacts. Despite this, it is speculated that life must have started around 3.8 billion years ago, when the LHB seized.
As mentioned in the previous post, the Archean period indicates, that earth has more water and minerals to make life plausible but, before that the atmosphere and the ocean has to form and cool off from HLB impacts. Only after this events, life could kick-start. Prebiotic chemistry happened during this time where the formation of lipids and peptides aggregates were formed. The idea of a “prebiotic soup” also must have happened here too. Many models were designed to imitate this period as well.
The protocell or LUCA (last universal common ancestor); could have emerged right after the prebiotic chemistry has taken place with metabolic diversification (which is about 3.8 -2.5 billion years ago). However, these are all scientific hypothesis, there are no fossilized records what so ever. Overall the origin of life idea is based on several hypothesis to build the prebiotic world and it’s chemistry. This grey area is where many chemical astrobiologist (like me) are focusing on. The idea however, is heavily supported by present knowledge of chemistry and geology with the power of models.
The earliest Stromatolites which is considered as the earliest micro fossils we have, is hypothesized (with heavy dispute) to have occurred right after this . The cyanobacteria rose with the power of photosynthesis giving an influx of oxygen to earth’s atmosphere, the very reason we have oxygen now. However, it should be noted that oxygen is toxic, meaning that other life forms utilizing non- oxygen metabolism during that time, must have went extinct without evidence. The Proterozoic eon starts here. The Cambrian explosion also starts here with the increasing of oxygen, leading to life forms which were well fossilized such as Opabinia and Marrella. Watch the video above to see how these creatures look like.
There are plenty of scientific evidence here. I will not be elaborating further on what happened after this. Many studies have been done, it is an establish science. We pretty much know what happened after the Cambrian explosion, but not what happened before that.
That’s all for now. The next post is about the possible sites of life’s origin.
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