From Memex to Hypertext by James M. Nyce & Paul Kahn

Author:James M. Nyce & Paul Kahn [Nyce, James M. & Kahn, Paul]
Language: eng
Format: epub
Amazon: B009K1X0ZC
Publisher: Academic Press
Published: 1992-02-03T23:00:00+00:00

How does a spider know how to spin?

Today we are calmer, at least on that front, and it is generally accepted that life began with the appearance of the first self-reproducing molecule. This is merely a chemical capable of assembling, from chemical fragments about it, an exact duplicate of itself. One can grasp what would happen when such a molecule appeared in a warm, complex sea, full of all sorts of simple nonliving chemical structures, existing thereby virtue of chemical processes and photochemical effects. These structures would have included such things as amino acids and nucleotides. (In the laboratory it has been demonstrated that such things show up when light shines on a chemical soup, chosen to be like the primeval seas as we envisage them.) A single molecule, able to build a twin from such a mess, would proliferate prodigiously until it had used up all the available primary material with which it could combine. It would not be interfered with by predators since, for a time, it would be all alone. But the process would not stop there. By chance, other replicating molecules would appear. Some of these would proliferate by seizing upon material already combined; thereupon the great process of evolution would be on its way. After millenniums, cells with all their internal intricacy would appear, then organisms made up of cells in combination, then fish and plants and mammals, and finally man.

This account is persuasive because so much of life, as we observe it today, depends upon replicatory molecules. All of heredity, as we now depict it, depends on the genes, which are self-duplicating nucleic acids. These pass the characteristics of an individual from one generation to the next. They control the development of an organism, from sperm and egg to adult, by molding messenger chemicals, which in turn mold the proteins: the hormones, enzymes, and the structural materials that constitute the body; those chemicals form and control your body and mine. The code by which the gene signals and controls is just now being deciphered in hundreds of laboratories. There is some question whether all this is sufficient to explain, for example, the linkages in the brain of a spider by which it knows how to spin a web without being taught, and so we may be taking only the first step on a very long road. But there is no doubt that the molding of one molecule by another lies at the basis of the wealth of life we see about us.

Man has not yet succeeded in creating life as here defined, but there is little doubt that he soon will. Some very simple short-chain nucleic acid, synthesized from inert matter and placed in a chemical soup, will suddenly assemble accurate images of itself and the job will be done.

We seem, thus, to have arrived at a concept of how the physical universe about us-all the life that inhabits the speck we occupy in this universe-has evolved over the eons by simple material processes,

Download

Copyright Disclaimer:
This site does not store any files on its server. We only index and link to content provided by other sites. Please contact the content providers to delete copyright contents if any and email us, we'll remove relevant links or contents immediately.