Five Billion Years of Solitude Read Online Free PDF Page A

noted that astronomers had already detected hydrogen, methane, ammonia, and water in clouds of interstellar gas and dust, and that even some varieties of meteorites were proving to be rich in organic compounds. All this suggested that planets with atmospheres similar to the early Earth’s would be common outcomes of planet formation, Sagan said. And, since the laws of physics and chemistry were everywhere the same, when warmed by their stars’ light these worlds would become enriched with life’s organic building blocks. Through innumerable iterations and permutations of organic compounds in the primordial soup, crude catalytic enzymes and self-replicating molecules would gradually emerge, and life’s genesis would be at hand. The rest of the group agreed: given hundreds of millions or billions of years, single-celled life would likely spring up on each and every habitable world, yielding an f l value of one.
    When the time came to discuss f i , the fraction of habitable, life-bearing planets that develop intelligent inhabitants, Lilly discussed his experiments with captive dolphins on the island of Saint Thomas in the Caribbean. Lilly began by noting that the brain of a dolphin was larger than that of a man, with similar neuron density and a richer variety of cortical structure. He recounted his various attempts to communicate with the dolphins in their own language of clicks and whistles, and told stories of dolphins rescuing sailors lost at sea. He focused on one case in which two of his captive dolphins had acted together to rescue a third from drowning when it became fatigued in the cold water of a swimming pool. The chilled dolphin had let out two sharp whistles in an apparent call for help, spurring the two rescuers tochatter together, form a rescue plan, and save their distressed companion. The display convinced Lilly that dolphins were a second terrestrial intelligence contemporaneous with humans, capable of complex communication, future planning, empathy, and self-reflection.
    Morrison broadened the discussion by introducing the concept of convergent evolution, the tendency for natural selection to sculpt creatures from very different evolutionary lineages into common forms to fit shared environments and ecological niches. Hence, fish such as tuna or sharks shared a streamlined body form with mammalian dolphins, and features such as eyes and wings had independently evolved across the animal kingdom several times. Perhaps, Morrison said, intelligence was another example of convergent evolution, and had emerged not only in humans and dolphins but also in other primates and cetaceans, such as whales and now-extinct Neanderthals. Like eyes or wings, intelligence might be an extremely successful adaptation that would emerge time and time again in a planetary environment—provided life first made the fundamental evolutionary leap from simple solitary cells to complex multicellular organisms. Moved by Morrison’s arguments, the Green Bank scientists optimistically placed the value of f i at one.
    Morrison also proved decisive in framing the Green Bank debate over the two final and most nebulous terms of Drake’s equation: f c , the fraction of intelligent creatures who would develop societies and technologies capable of interstellar communication, and L , the average longevity of an advanced technological civilization. He first noted that while creatures like dolphins and whales might well be intelligent, in their current aquatic forms they seemed destined for cosmic invisibility: supposing they had language and culture, they still lacked a way of assembling or using even relatively simple tools and machines. None of the attendees could easily imagine any cetacean civilization ever building anything like a radio telescope or a television broadcast antenna. But on land, Morrison said, history suggested that the emergence of technological societies might be another convergent phenomenon. The early civilizations of