Dyson favoured the dual origin theory: that life first formed as cells, then enzymes, and finally, much later, genes. This was first propounded by the Russian biochemist, Alexander Oparin. J. B. S. Haldane developed the same theory independently. In Dyson's version of the theory, life evolved in two stages, widely separated in time. Because of the biochemistry, he regards it as too unlikely that genes could have developed fully blown in one process. Current cells contain adenosine triphosphate or ATP and adenosine 5'-monophosphate or AMP, which greatly resemble each other but have completely different functions. ATP transports energy around the cell, and AMP is part of RNA and the genetic apparatus. Dyson proposed that in a primitive early cell containing ATP and AMP, RNA and replication came into existence only because of the similarity between AMP and RNA. He suggested that AMP was produced when ATP molecules lost two of their phosphate radicals, and then one cell somewhere performed Eigen 's experiment and produced RNA.