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What Is Life? A Closer Look

California Institute of Technology
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  • Feature Articles
  • Astronomy
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What Is Life? A Closer Look by Robert l. Sinstieimell' (On Seminar Day in April 1967, Robert L. Sinsheimer, then professor of biophysics at Caltech, delivered a talk entitled "What Is Life?!! (published in the Caltech Quarterly, a short-lived spin-off of E&S). At the dawn of the era of space exploration, many people were wondering how life was to be recog- nized if indeed it were found elsewhere than on Earth. Sinsheimer gave the biologist's definition. Now, 30 years later, he sticks by his answer, and fills in some gaps with data from current biological research.) The black box (or, more accurately, the colorless capsule) that we call a living cell is a specialized, intricate, highly evolved machine. Nearly three decades ago we were first able to describe qualitatively the essential elements of this self-perpetuating machine (Caltech Quarterly, Summer 1967) at the level of its molecular orga- nization. At that time our understanding of the machinery of life waS newly emergent, still quite incomplete and porous, but sufficient to replace the older vague theories and speculations. Back in 1967 we were asking: What is the essence of this quality, "life"? Biology is the science of life, but no biology textbooks could provide a definition of what life is. There were two explanations advanced to account for the properties of living beings: one postulated that the substance of living matter was intrinsically different from that of nonliving matter; the other, that the properties of life were solely a conse- quence of an unusual organization of ordinary matter in living creatures. The latter argument had been hampered by the inability to describe We can actually classify and enumerate the components of the machine, gene by gene, and discern their interrelated functional organization. that organization, but by 1967 biologists were able to describe the complex organization of the cell, the basic unit oflife, in physical and chemi- cal terms. I wrot

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