9781422283349

We may never really know how life began, but that hasn’t stopped people from making all sorts of suggestions. Many people believe that something as complex as life must have been created by an all-powerful supreme being. Such points of view cannot be discussed scientifically, however. Some people have suggested that life didn’t begin on Earth at all but came here from outer space, perhaps in the form of bacteria or viruses carried on a meteorite. But if life didn’t begin on Earth we still have to answer the question of how it began somewhere else. We wouldn’t be any further forward. Chapter THE BEGINNING OF LIFE CONDIT IONS FOR L I FE First let’s try to imagine what conditions were like on Earth before there was any life. Four billion years ago the Earth was a distinctly unpleasant place to be. It was a mere 600 million years old at this time and its surface was being constantly bombarded by the rocky debris left over when planets formed. Vast

amounts of gas and steam poured out from hundreds of volcanoes, forming the Earth’s first atmosphere. There was very little, or no, oxygen. As the Earth cooled, the steam condensed and fell in torrential rainstorms to form hot oceans. This must have been accompanied by spectacular lightning displays and continuous crashes of thunder. There was nothing in the early atmosphere of the Earth to prevent high-energy ultraviolet radiation from the Sun reaching the surface. This energy may have continually rearranged the molecules in the oceans until eventually some appeared that would lead to the formation of life.

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