In 1953 L.S.Miller succeeded in synthesizing, in an abiotic way, various organic substances and among these many amino acids, components of our proteins. This experiment also seemed a confirmation of the theory of the prebiotic mixture. The discovery created great enthusiasm among scientists and it seemed, at that period, that in a short time the test-tube synthesis of life would also arrive. But soon, some obstacles resulted insurmountable and hence after more than fifty years we are no further than Miller’s experiment. Starting from these experimental data the author, in this essay, presents the result of 25 years’ research on prebiotic chemistry. In particular he illustrates experimental indications on: the selection of the natural amino acids and the disappearance of the amino acid Dexter, the origin of a rudimental genetic code and the interdependence nucleic acids – proteins. These data indicate that life probably had its origin on firm land, that the prebiotic mixture never existed, and they also create much doubt on the existence of an ancestor common to all living organisms. In conclusion thetheory on the origin of life is presented.