1.3 billion years ago
According to the Book of Genesis, God halted construction of a majestically high tower in Shinar by introducing many languages. The Tower of Babel never reached heaven because its builders, stripped of their common tongue, became confused. This parable shows the importance of a universal language. While people still speak in many languages (though fewer as time goes by), the genetic code--the translation of genes into proteins--is everywhere the same. The common denominator of life extends further. Only about twenty different amino acids, linked in chains of a few dozen to several hundred, make up the proteins in all known organisms on Earth. The amino acid sequence, primarily, determines the protein's shape, and the shape determines its function. The code for translating the sequence of nucleotides in DNA to a sequence of amino acids in a protein is nearly universal. In almost all cases, a given nucleotide sequence will translate into the same amino acid sequence. Mutations are heritable changes in the quantity or sequence of DNA bases. A mutation occurs when something in the environment--radiation, say--either breaks a chemical bond or forges an uncalled-for one, and the resulting change in the DNA sequence, which confers new abilities or disabilities, is copied and passed down through the cell's descendants or causes the cell's demise. Like the dfference of an "s" between teh words laughter and slaughter, small changes or additions can have synergetic effects. The tiny Archean sacs of DNA and RNA carried out their activities prodigiously. With sleep unknown to them they grew, consumed energy and organic chemicals, and divided incessantaly. Their colonies and fibers interconnected and covered the sterile globe in a spotty film. Bacteria first expanded in the waters, where they modified the liquid and produced gases. Then they expanded to the surfaces of the sediments, where they still survive. Today the biosphere surrounds the Earth from a little deeper than six miles into the ocean to over seven miles up, above the mountaint tops at the top of the lower atmosphere. Learn More
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