THE MAJOR TRANSITIONS IN EVOLUTION (W. H. Freeman, 1995)
(Copyright © 2000 Piero Scaruffi | Legal restrictions - Termini d'uso )
| The key to evolution is heredity: the way information is stored, transmitted and translated. Evolution of life as we know it relies on information transmission. And information transmission depends on replication of structures. The authors believe that evolution was somewhat accelerated, and changed in character, by and because of dramatic changes in the nature of biological replicators, or in the way information is transmitted by biological replicators. New kinds of coding methods made possible new kinds of organisms. Today, replication is achieved via genes, that utilize the genetic code. The authors argue that this is only the latest step in a story that started with the earliest, rudimentary replicators, the first genes. The first major breakthrough in evolution, the first major change in the technique of replication, was the appearance of chromosomes: when one gene is replicated, all are. A second major change came with the transition from the solitary work of RNA to the dual cooperation of DNA and proteins: it meant the shift from a unitary source of replication to a division of labour. Metabolism was born out of that division of labour and was facilitated by the chemical phenomenon of autocatalysis. Autocatalysis allows for self-maintenance, growth and reproduction. Growth is autocatalysis. Early, monocellular organisms (prokaryotes) evolved into multicellular organisms (eukaryotes). The new mechanism that arose was gene regulation: the code didn't simply specify instructions to build the organism, but also how cells contributed to the organism. Asexual cloning was eventually was made obsolete by sex, and sex again changed the rules of the game by shuffling the genetic information before transmitting it. Protists split into animals, plants, fungi, that have different information-transmission techniques. Individuals formed colonies, that developed other means of transmitting information, namely "culture; and finally socail behavior led to language, and language is a form of information transmission itself. Each of these steps "invented" a new way of coding, storing and transmitting information. |
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