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30 A New Era According to Hoyle and Wickramasinghe, evolution proceeds in bursts of activity stimulated by the arrival of new genes from the sky. They cited in particular a single event 570 million years ago, perhaps a collision with comet fragments or a molecular cloud, that may have deposited organisms on the Earth that provided most of the genetic information that now char- acterizes Earth life. They described mutations, gene doublings, and recom- binations as no more than fine-tuning superposed on the much greater cosmic assembly process. Mind-Stretcher. Instead of seeing life as a collection of isolated pockets, Hoyle saw it as a coherent whole developed out of a single aggregate of cosmic genes. If all life-forms in our galaxy share a common genetic heri- tage, that could make life everywhere vulnerable to the same biological threats to their health—including diseases from space. Earth continues to receive ready-formed living structures such as bacte- ria and viruses, these scientists argued. In their conception, the primitive Earth may have been transformed into a habitable condition mainly due to contributions from comets, which created the primordial oceans and atmosphere. Wickramasinghe noted that 100 tons of cometary material reaches Earth every day. Hoyle suggested that peptide chains might reproduce in interstellar space, possibly becoming clumps that consume others and expel waste. He proposed that microorganisms set the right physical conditions within clouds of interstellar gas so that suitable stars and planets form. Hoyle and Wickramasinghe even claimed that cosmic bacteria, or superstructures built from them, may be in control of our galaxy. The surest way for such bacteria to prosper would be by maintaining a firm grip on the interstellar magnetic field.” Wickramasinghe still was advocating these theories in 2002, after Hoyle had passed on. He argued that we should extend the boundaries of Darwin’s warm little pond to encompass the largest possible amount of carbonaceous material in the cosmos. “Life,” he concluded, “would inevi- tably develop on every habitable planet, descended from the same all-per- vasive genes.”** Most scientists remain skeptical of these theories. However, Deamer found space delivery of amino acids billions of years ago a plausible com- panion to organic synthesis in the atmosphere.”* The transfer of life to the Earth might be local. The famous physicist Lord Kelvin suggested in 1871 that an astronomical body might strike a planet with enough force to blast debris out of its gravitational field. As a result, The Mars Rock