The first life evolved more than 3.5 billion years ago. Scientists estimate that the Earth is some 4.5 billion years old. For nearly the first billion years after the Earth formed, the planet was inhospitable to life. 3.8 billion years ago, the Earth's crust had cooled and the oceans had formed and conditions were more suitable for the formation of life. Montessori Science, Montessori Elementary, Evolution, Prehistoric World, Life On Earth, Palaeontology, World View, Life Form, Science For Kids