Habitable Earth

    Earth was formed around 4.6 billion years ago, yet animals did not emerge until six hundred million years ago. While six hundred million may seem like a big number it is only fifteen percent of the earth’s history. So what exactly was happening on our planet for eighty five percent of its history? 3.6 billion years ago single celled organisms began to form and they ruled the planet for around three billion years. 

    Now we still have a billion years of unanswered questions. Who ruled the earth for the first twenty two percent of its history? How did life first begin to form on earth? How did single celled organisms evolve into the wide variety of plant and animal life on this planet? What did earth look like when single celled organisms ruled the earth?

For the first twenty two percent of earth’s existence the oxygen levels were too low to support life. How do we know what earth’s oxygen levels were four billion years ago? The reason we know not only of things such as earth’s historical oxygen levels, but how we know that single celled organisms once ruled the earth, how we know that animals emerged only six hundred million years ago, and how we know that the earth is not six thousand years old; the reason why is sedimentary rocks.  

Sedimentary rocks are carriers of physiological history, a type of history we often forget about. How exactly do we know that these rocks carry physiological history? Sedimentary rocks are layered, and by breaking apart the layers of these rocks we discover by examining the rocks physical features. How do we know that everything the rocks have taught us is true and will not be later proven false? This is a question I can’t answer, and as one of the professors said in the video, that if we had no unanswered questions, then we would have no need for scientists? 

How exactly did life evolve on this planet? Six hundred million years ago due to a drop in the earth’s oxygen levels the entire planet froze over into what we now know as, the ice age. During the ice age glaciers began to form in what we now know as Namibia(where Namibia is currently located was part of the ocean at that time of Pangea). This was one of the hottest places on earth, and the glaciers did not form out of mountains, but rather they formed out of the ocean. 

Five hundred thirty million years ago a shift in the earth’s tectonic plates caused the Cambrian Explosion, which lead to two things. The first is a rise in oxygen levels leading to the frozen earth melting, which ended the ice age. The second is the creation of multi celled organisms. From there, multi celled organisms began to evolve into the vast lifeforms that live on earth today.