Life is valuable to all of us, but how it began is not something many people are interested in discussing. This is a brief summary of one version the history of life on Earth, agreed on by most biologists. The Earth's crust formed about 4.5 billion years ago. There are various theories as to what it was that caused the first prokaryotic cells to form 700 million years later. Unfortunately, Scientists have not agreed on what it …showed first 75 words of 514 total…

…showed last 75 words of 514 total…the Tertiary period (65-1.8 mya), Australia began to drift northward. Mammals spread extensively and flowering plants dominated forests. The Quaternary period (1.8 mya - present) has two epochs. The Pleistocene was time of sudden climatic changes and extensive glacial formation. The Holocene started about 15,000 years ago and continues today. So there you have it. For all those people who say, "how could we have possibly evolved from a stupid little amoeba?" this is one plausible explanation