0.8 billion years ag (The Proterozoic Eon)
The height of the Proterozoic Eon was some 800 million years ago. This was still before the famous Cambrian explosion. Part of what led to the astonishing radiation of life forms today was sex--not two-parent sex leading to reproduction as we know it in mammals, but a more primordial kind. The first sort of sex to appear on our planet was the bacteria-styl genetic transfer exploited by today's genetic engineers. In this sort of sex anywhere from a few to almost all of an organism's genes can go to its partner. Bacteria-style sex was important as a way of genetically locking together symbiotic mergers between very different organisms. And it was always crucial to the biota's "reaction time": its abilitiy to respond quickly to environmental changes and emergencies. Human beings and most plants and animals simply cannot make dramatic changes in their outward appearance or metabolism by receiving visiting genes that code for at most only a few percent of their proteins. Yet in the microcosm, the implications of easy genetic exchange are staggering. For if, indeed, all strains of bacteria can potentially share all bacterial genes, then strictly speaking there are no true species in the bacterial world. All bacteria are one organism, one entity capable of genetic engineering on a planetary or global scale. In the words of Canadian bacteriologists Sorin Sonea and Maurice Panisset, this entity is, in effect "a unique, complex type of clone, composed of highly differentiated (specialized) cells." During the Proterozoic, before more familiar organisms such as the trilobites evolved, strange beings appeared which may or may not have been animals. Learn More
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