- 2106 - EVOLUTION - How Did I Get Here?? Earth is finely tuned for life. How did it get that way? Are we here as a result of random collisions and mutations? We only know life that is us. That is a sample size of one. Regardless, Earth's history demonstrates that life can take root and evolve. Here is what we have learned.
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------------------ 2106 - EVOLUTION - How Did I Get Here??
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- It is an amazing story. You may find it hard to believe. It all started 13,800,000,000 years ago when the Universe started expanding. Energy and matter are two forms of the same thing. But we needed matter to form stars. Stars happened about 13,000,000,000 years ago with only about 0.03% of all the mass/energy in the Universe
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- Originally the stars were made up of only hydrogen and helium. Giant stars were crushed by gravity. When atoms themselves got crushed into a rebound that resulted in a giant explosions, called a supernovae.
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- It took billions of years of repeated star formations and star explosions to create enough heavy elements out of the merging of protons and neutrons and electrons into the elements. We find all these elements in the Periodic Table of Elements today. Those elements are what was needed to form our Sun and planets in our solar system.
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- Our Sun happens to be in a perfect zone in our Milky Way Galaxy. It was in the right position to allow the formation of rocky planets that could orbit around it. The Earth got lucky because it orbits the Sun at just the right position to host liquid water at the right temperature.
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- The Earth also lucked out having a metallic core and a powerful magnetic field. That magnetic field protected the surface from being bombarded by harmful radiation. The plate tectonics at the surface were active enough to replenish the Earth's surface with nutrients and to stabilize the temperatures. Our Moon was likely responsible for keeping Earth's tilt at 23.5 degrees. This allowed the seasons and the changes needed for the diversity of life on Earth.
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- 3,400,000,000 years ago these conditions allowed a single celled organism called a prokaryotes to form. But, it took another 2 billion years before there was a merging of these cells and another billion years before multi cellular life formed. These multi cellular life forms proliferated 550,000,000 years ago. It is what is called the Cambrian Era Explosion.
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- Somehow we got from multi cellular life to the development of an intelligent species. We somehow advance enough for me to write this Review. Somehow we humans advanced far beyond our close animal relatives. Somehow our species escaped extinction several times in the process.
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- Astronomers have found thousands of planets orbiting other stars and they have found billions of more stars in billions of more galaxies. Given the sheer numbers could the Earth really be unique among so many planets?
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- But the Earth must be unique with very rare conditions that would allow the evolution of life. From that aspect we might very well be irreproducible? We come from a long chain of implausible coincidences.
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- We have good reason to conclude that we are only technological civilization in our own galaxy.
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- Our Sun contains 71 % hydrogen, 27% helium, and only 2% of the rest of the elements in the Periodic Table of all elements. The Earth and the other planets formed out of that small 2% of construction material.
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- Then there are these extinction events: We have seen Gamma-Ray Bursts in other galaxies. From these observations astronomers predict that our Milky Way galaxy would experience such an event every 1 to 100 million years. A single burst would sterilize most of the galaxy.
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- The habitable zone in our galaxy extends only 23,000 to 30,000 light years from the galactic center. We just happen to be 24,500 lightyears from that center. At the same time we just happen to be within the habitable zone of our own solar system. Liquid water is the basic sign for habitat and Venus and Mars orbiting on either side of us are missing liquid water.
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- Plate tectonics on Earth's surface brought nutrients to the surface to replenish that depleted by living cells. These tectonics were necessary to recycle carbon and to stabilize temperatures over long time scales. Earth's magnetic core and rapid rotation shielded the surface from harmful radiation. Without the shield the atmosphere would have eroded and the surface would have fried.
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- Scientist believe the Moon was responsible. The giant collision that splashed the Moon into orbit also created Earth's metallic core and its floating crust. The relatively large moon orbiting Earth was a type of stabilizer allowing Earth's axis not to wobble in its orbit. T he Earth - Moon partnership is a rare happening. Without it we would likely not be here.
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- Once all this planetary juggling settled down somehow life started. Single cell organisms in rocks have been dated to be 3.4 billion years old. The Sun and Solar System formed 4.5 billion years ago. That is when life started, but, it remained at the microbe level for the next 3 billion years. In fact, those same microbes are alive with us today.
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- These simple cells are called prokaryotes. They are merely a bag of jelly containing the molecules of life, we call DNA. The more complex cells are called eukaryotes. They first came on the scene 1.5 billion years ago.
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- Somehow after 3 billion years these primordial single cells merged into organisms called bacteria and archaea. Somehow these guys started eating each other and using their raw materials to grow and multiply. Life started from these simple cells. At this cellular level there is no difference between your cells and those of a mushroom, or any other life on Earth.
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- The eukaryotes forming multi cellular organisms did not happen until 550 million years ago. This outburst of life forms is known as the Cambrian Era. How it got to humanity is written in our genes. One conclusion from analysis of these genes is that chimpanzees living in central Africa differ from one another genetically no more than humans do living from opposite ends of the world. This means that both started out from their same gene pool.
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- Some 150,000 years ago the human gene pool was reduced to a few thousand, a few hundred breeding pairs. Some 70,000 years ago our population on Earth was again reduced to about 1,000. The 7 billion people on Earth today are descendents of this small group. How likely is our advancement to the technological society we have today likely to get repeated.
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- Could this really happened somewhere else in our galaxy? How likely is 4 billion years of a chain of events likely to repeat itself? It all suggests that we are unique on our planet and even in our own Milky Way Galaxy. All the more reason to take care of what we have. It will be hard to repeat it.
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- Are life's beginning on Earth so convoluted and unlikely that we are alone in the entire Universe? Yet somehow life began on Earth as soon as it was possible to begin. The molten Earth had barely cooled enough. Immediately when asteroids and comets stopped pummeling Earth 4 billion years ago life got started.
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- We are here for a purpose. One purpose is to try and understand all of this. Our knowledge is but a few seashore pebbles on the sand with a whole ocean of unknown before us. I'm working on it. Hope you learned something?
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- September 24, 2018
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--------------------- Thursday, July 11, 2019 -------------------------
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