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Book details
  • Genre:SCIENCE
  • SubGenre:Life Sciences / Evolution
  • Language:English
  • Pages:196
  • eBook ISBN:9798350911077

The Modern Synthesis of Evolution with Genetics

by Wayne Douglas Smith, Ph.D.

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We have to date from 1859 (On the Origin of Species) as the beginning of modern thought. For what Charles Darwin did was to offer a world-picture totally different from that which had satisfied the mind of humankind before that date. We had supposed that it was a world of order, moving under divine guidance and omnipotent intelligence to a just and perfect fulfillment in which every virtue would find its fit reward. But Darwin, without attacking any creed, described what he had seen. Suddenly the world and nature seemed to be only a place of slaughter and strife in which birth was an accident, and only death was a certainty. Nature became natural selection: that is, a struggle for existence. And not for existence only, but for mates and power, and a ruthless elimination of the unfit. The surface of the Earth seethed with warring species and competing individuals. Every organism was the prey of some larger beast, and every life was lived at the expense of some other life. Great natural catastrophes came, and millions of living things were weeded out and killed. This was evolution. Darwin had reduced a human to an animal fighting for his transient mastery of the globe. Man was no longer the son of God; he was the son of strife. His wars made the fiercest brutes ashamed of their amateur cruelty. The human race was no longer the favored creation of a benevolent deity. It was a species of apes, which the fortunes of variation and selection had raised to a precarious dignity, and which in its turn was destined to be surpassed and to disappear. Man was not immortal. He was condemned to death from the hour of his birth. Imagine the strain upon the minds brought up with the tender ideas of youth and forced to adapt themselves to the harsh and bloody picture of a Darwinian world. Is it any wonder that the old faith is fighting fiercely for its life. Do the victors (the evolutionist) sit sadly amid the ruins, secretly mourning their triumph, yearning f
In the beginning, there was only chemistry on the Earth. There were no minds, no creativity, and no intention. Nevertheless, once self-replicating chemicals had a chance to arise, there would have been an automatic tendency for more successful variants to increase in frequency at the expense of less successful variants. Success in chemical replicators is simply synonymous with frequency in circulation. A successful replicator molecule will be one that has what it takes to get duplicated. DNA, which is a self-replicating material present in nearly all living organisms, is so uniform that it consists of variations in sequence of the same four proteins: A, T, C, G. Although the products developed by DNA sequences are almost infinitely variable (creating brains for mammals, wings for birds, and leaves for plants), the recipes for building these products are just permutations of A, T, C, G. With DNA, there arose a self-copying system in which there was a form of hereditary variation, with occasional random mistakes in copying. The consequence was that the planet Earth came to have a mixed population, in which variants of life competed for resources. Resources will be scarce, or will become scarce when the competition heats up. Some variant replicants will turn out to be relatively successful in competing for scarce resources. Others will be relatively unsuccessful. So now we have a basic form of natural selection. To begin with, success among rival replicators will be judged purely on the direct properties of the replicators themselves: for example, on how well their shape fits their template. But after many generations, replicators survive not by virtue of their own properties, but by virtue of causal effects on something else, called phenotype. Phenotypes are parts of animal and plant bodies that genes can influence. Phenotypes are the way replicators manipulate their way into the next generation. More generally, phenotypes may be defined as consequences of replicators that influence the replicators' success, but are not themselves replicated. The chemical world in which a gene (which is the heritable unit in DNA) does its work is not the unaided chemistry of the external environment. The necessary chemical world in which the DNA replicator has its being is a much smaller, more complicated bag: the cell. The chemical microcosm that is the cell is put together by a consortium of thousands of genes. The simplest of autonomous DNA copying systems on the Earth are bacterial cells, and they need at least a couple hundred genes to make the components they need. Cells that are not bacteria are called eukaryotic cells. Our own cells, and those of all animals, plants, and fungi, are eukaryotic cells. They typically have tens of thousands of genes, all working as a team. It seems probable that the eukaryotic cell itself began as a team of a few bacterial cells that joined up together. All genes do their work in a chemical environment put together by a consortium of genes in the cell. The next threshold in life on Earth is an increase in the speed at which information is processed. In the animals, this is achieved by a special class of cells called neurons, or nerve cells. Predators can leap at their dinner and prey can dodge for their lives, using muscular and nervous organs that act at speeds hugely greater than the embryological machinations at which the genes put the apparatus together in the first place. Among the consequences of high-speed information processing may be the development of large aggregations of data-handling units, which we call brains. Brains are capable of processing complex patterns of data apprehended by the sense organs, and capable of storing records of them in memory. A more elaborate consequence of crossing the neuron threshold is a conscious awareness. Many philosophers believe that consciousness is crucially bound up with language.
About the author
Wayne Douglas Smith studied at the College of William and Mary in Virginia, concentrating in physics and psychology. He earned a Ph.D. in clinical psychology and was employed as a psychologist for forty years. Wayne lives in Virginia Beach with his wife, the environmentalist Kayle Warren.