Question: is there any solid evidence that states that we did infact develop from a micro-organism.

Dave Underhill answered on 12 Jun 2019:

yes absolutely there is. We know that the earliest evidence for micro-organisms is about 3.5 billion years old (found in what is now Australia) (https://news.wisc.edu/oldest-fossils-ever-found-show-life-on-earth-began-before-3-5-billion-years-ago). whilst this life was essentially single celled this evidence already shows that it was quite diverse – suggesting it first appeared earlier. For the next about 3 billion years all life was micro-organisms! it is only in the last 500 million years or so that more complex life forms have evolved.

Micro-organisms reproduce so fast that they can evolve really quickly (which is why you can find micro-organisms in virtually every climate on the planet!). However, despite this there was a lot for them to evolve in order to allow the development of more complex life forms such as ourselves, photosynthesis being perhaops the most important – and this took approximately 500 million years to evolve. After about anouther 500 million years (so about 2.5 billion years ago) we see what is called the great oxygenation event – basically for 500 million years minerals had been absorbing all of the oxygen produced by the photosynthesis, but when these minerals couldnt soak up any more the oxygen began to accumulate in the atmosphere. So now we have oxygen but all we have still is essentially single celled orgainsims and colonies. Over the next billion years we get various changes – evolution is random and has more dead ends and false starts than success! By 1.2 billion years ago we see different sexes arise in single celled organisms. By 1 billion years ago we see the first plants appear, they were multicellular and photosynthesising but not what we would reconise as plants – these are found on land about 800 million years ago. perhaps unsuprisingly it is at a similar time that we see the first life forms which feed on organic matter such as other micro-orgaisms (about 750 million years ago). These were single celled initially but they are considered to be the first animals (protozoa). so the earth is 4.5 billion years old and it has taken 3.75 billion years for life to evolve into plants and animals! However, it would be another 250 million years before we start to see the emergance of complex multi-cellular life. This is probably related to the fact that it was only by about 600 million years ago that there was enough oxygen to form an ozone layer which helps reduce the dangerous UV radiation from the sun. Only at this point was the colonising of land really possible! However, it maybe that this had wider concequences as it is around the same time that we see the first complex multi-cellular life. Now things really pick up! at around 550 million years ago we have what is called the Cambrian explosion which is where we see the apperance of skeletons and the arrival of virtually all the different body shapes we see today.

all of this becuase some single celled micro-organisms developed the ability to produce the glucose they needed to survive from water, carbon dioxide and sun light, giving off oxygen as a byproduct!