Abstract. The Big Bang model is the widely held theory of the evolution of the universe from a state of extremely high temperature and density that occurred 13.7-13.8 billion years ago. The solar system, Sun and planets, was formed ~4.5 billion years ago. For more than a billion years there was no biological life on the surface of the Earth. Now scientists know that primitive life began at least 3.5 billion years ago (discovery of oldest rocks with fossil evidence of life on Earth). Life on Earth was developed inside water (to be protected from the damaging UV radiation) and was very simple, microbial in size. The Cambrian explosion was a crucial period of rapid evolution in complex animals that began roughly 540 million years ago. Scientists investigated the evidence of Cambrian explosion which was significantly correlated with surges in Oxygen levels and followed by bursts in animal evolution and biodiversity. The pace of life’s transformation abruptly accelerated with the appearance of nearly all major animal groups alive today. It was an extraordinary and baffling episode in evolutionary history. Why animal life got more complicated in such a hurry remains a burning question for paleontologists and evolutionary theorists. Was it just a matter of evolving the right combination of genes? There is strong evidence that aerobic organisms were developed when more oxidizing energy was available with increased concentration of O2. The process of metabolizing food in the presence of O2 releases much more energy (10-16 times, in mitochondria) than most anaerobic pathways. Animals rely on this potent energy to drive evolutionary innovations as muscles, nervous systems, mineralized shells, exoskeletons and teeth. Scientific evidence by an international team of paleontologists, biochemical modelers and chemists offered detailed support for the idea that Oxygen levels and animal diversity (540 years ago) are positively linked, but with a twist. Instead of oxygen levels gradually increasing, Cambrian seas underwent rapid periods of oxygen booms and busts. These rapid fluctuations in Oxygen are correlated to bursts of diversification and extinction during the Cambrian explosion. Also, there is plentiful scientific literature on the subject of the fundamental role of Reactive Oxygen Species (ROS), free radicals and increased concentration of O2 in atmosphere and oceans in triggering the evolutionary animal biodiversity during the Cambrian Explosion. Although there also are factors, higher Oxygen levels were required to promote the explosive evolutionary animal radiation during the Cambrian period.