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Meaning of life1/31/2024 He called this his PICERAS definition of life, where PICERAS was an acronym for “program, improvisation, compartmentalization, energy, regeneration, adaptability, and seclusion.” Unfortunately, a single rabbit remains dead if the listed elements must all be present, while the mated pair remains alive. He set out an alternative definition of “life” that listed items that he thought were needed to give life the features that he valued. Koshland, distinguished as an experimental biochemist, dug the hole a bit deeper as he tried to manage the problem that his committee had created. Using language precisely, one rabbit may be alive even though he or she is not life. But those living parts need not be coextensive with a living system and need not represent life. Parts of a living system might themselves be alive (a cell in our finger may be “alive,” as might a fertilized ovum in utero). Rather, it represents the conflation of a part of a system with its whole. The “elite” have confused the concept of “being alive” with the concept of “life.” This is not simply the mistaking an adjective for a noun. ![]() The imprecise use of language is manifest. Two rabbits-a male and female-are alive but either one alone is dead.” At that point, we all became convinced that although everyone knows what life is, there is no simple definition of life. ![]() Everyone nodded in agreement that the essentials of a life was the ability to reproduce, until one small voice was heard. Is an enzyme alive? Is a virus alive? Is a cell alive? After many hours of launching promising balloons that defined life in a sentence, followed by equally conclusive punctures of these balloons, a solution seemed at hand: “The ability to reproduce-that is the essential characteristic of life” said one statesman of science. What is the definition of life? I remember a conference of the scientific elite that sought to answer that question. As president of the American Association for the Advancement of Science (which publishes the prestigious journal Science), Koshland recounted his own experience with a committee that was charged to generate a definition of life: Also not new is a certain imprecision in the language used to address this question and therefore an imprecision in the consequent ideas.ĭaniel Koshland recently provided an anecdote that illustrates this imprecision (Koshland, 2002). The question is hardly new, nor is the recognition of its difficulty. Astrobiology 10, 1021–1030.Ī strobiologists are committed to studying life in the Cosmos, the terran life we know as well as the extraterran life we do not know but hope to encounter. Key Words: Evolution-Life-Life detection-Biosignatures. Last, we ask what chemical structures might support Darwinian evolution universally these structures might be universal biosignatures. ![]() And we consider how a definition centered on Darwinian evolution might itself be forced to change as supra-Darwinian species emerge, including in our descendents, and consider the chances of our encountering supra-Darwinian species in our exploration of the Cosmos. We also look at how constructive beliefs about biosignatures change as observational data accumulate. Accordingly, this article discusses various definitions of life held in the astrobiology community by considering their connected “theories of life.” These include certain “list” definitions and a popular definition that holds that life is a “self-sustaining chemical system capable of Darwinian evolution.” We then act as “anthropologists,” studying what scientists do to determine which definition-theories of life they constructively hold as they design missions to seek non-terran life. Any definition is intricately connected to a theory that gives it meaning.
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