The four big etiological questions: How did the universe as a whole come about? What is physical matter and how did it originate? How and when did life begin? And how did human beings come to exist?
None of these questions could be answered until enormous amounts of scienti?c knowledge had been gathered and correlated. So these questions were raised with celebrated practical myths.
The beginnings of the science of biochemical evolution are associated primarily with the work of three men. In 1922 a Russian biochemist, Alexander Oparin, In 1928 the English biologist J.B.S.Haldane. Then in 1953 the American biochemist Stanley Miller.
Oparin had theorized that during the Earth’s early stages a variety of organic compounds developed out of inorganic materials. He described theoretically how these compounds could develop into the ?rst prevital cells and then into living organisms. As the crust of the Earth began to form and the temperature of the atmosphere dropped below a thousand degrees (Celsius), a variety of chemical reactions took place including torrential rains, lightning which formed hot pools of water containing organic compounds that washed down from the atmosphere. As a result, over the span of a billion years—mixtures of hydrocarbons, nitrogen, hydrogen, and ammonia continually produced endless variety of organic compounds that formed complex molecules creating building blocks of living cells. At this stage the Earth was covered with what Haldane called a “hot dilute soup” in which these reactions were taking place. With the synthesis of proteins the ?rst steps had been taken toward the development of life. The ?rst experimental support for Oparin’s theory came from Miller’s experiments at the University of Chicago. Miller introduced methane, ammonia, and hydrogen into a simple glass apparatus. The circulating gases represented the early atmosphere, the ?ask of boiling liquids represented the new oceans. After one week of the experiment the gases were pumped out and the brownish liquids were analyzed. He found that a variety of organic compounds had formed along with several amino acids which were not random selection but included substances from living organisms. Miller believes that “almost certainly they became important for the metabolic processes leading to ATP synthesis early in the evolution of life .
With such other descriptions it sounds as though these experiments are producing live organisms, it must be emphasized that they are not living—yet.
The solar system was born 5 billion years ago, and a half-billion years later our planet had become a dense, round, hot ball and still inhospitable. From the fossil record we know that the ?rst hard-shelled animals emerged 700 million years ago, and continued to diversify in number of species. We can be certain that soft-bodied animals, including countless species of single-celled organisms , passed through a history of evolutionary development. The oldest known forms of life are alga like cells that lived 3.5 billion years ago. These cells were capable of photosynthesis. The fossil records indicate that life developed sometime between 4.5 billion years ago—when the Earth was formed.
Since the time that living organisms ?rst emerged from the “hot thin soup, ”the spread of species is vast. Taxonomists have so far discovered, 1.5 million species of living organisms, and some ten thousand new species are added annually to the list. It is estimated that on our planet perhaps ten million species of organisms exist today, yet this number is less than 1 percent of all the species that have existed on Earth since life began. Scientists guess that perhaps one out of ?ve thousand to ten thousand extinct species show up in the fossil record. Evolution produced ten billion species on Earth since the planet’s beginning.
The theory about the origin of life —panspermia suggests that life may exist throughout the universe and that living substances journeyed to our planet from some other location. Even if this is true it doesn’t solve the problem of how life began. It only pushes the problem away to some unknown location. The theory of spontaneous generation was believed for thousands of years until the experiments of Louis Pasteur proved it false. This theory held that fully developed species are generated out of nonliving materials, eg frogs from mud.
Hylozoism is the belief that all matter is alive. It was held by the earliest Greek philosophers and passed by occasional theorists ever since. Creationism is the belief that life can originate only by a touch of the supernatural, and vitalism is the hypothesis that a special “life-force” must infuse nonliving matter before it can come alive. Both theories are still widely held, but their possibility depends partly upon whether it can be shown that living organisms can develop from inorganic matter.
At present, it appears that “life” can be de?ned with two qualities: self-replication and mutability. These two characteristics include the essential processes of evolution: continuity and adaptation. An organism must be able to replicate and produce to assure continuity of its species. But mutability—the ability to effect changes from one generation to another and adapt to a ?uid environment—is essential for survival. Species must be able to change along with their environments. So far as we know, only living organisms have these two qualities .It has been noted that mineral crystals and ?ames of ?re can reproduce; they both effect replication of their own kind without affecting themselves. In addition, ?ames display a sort of metabolism: they ingest material, digest it, and excrete wastes.
Motility—the ability to move about. Metabolism—the ability to ingest materials, digest them) ,and excrete wastes. Growth—the ability to proceed through some sort of life-cycle. Irritability—the ability to react to external stimuli, a ?rst step in adaptation. Dynamic equilibrium—the ability to maintain a stable internal condition within changing external conditions (such as adjusting to temperature).
Charles Darwin formulated a non challenging theory about the concept of natural selection in The Origin of Species in 1859 . It had been noted that trait changes take place from parent to offspring and that these variations are often inherited. Selective breeding of domestic animals and plants had long been practiced. Following Darwin’s theory of natural selection from the struggle for survival, there were two large gaps in people’s understanding of how evolution works. First, heredity, the transmission of speci?c characteristics from parents to offspring was by genes which followed predictable patterns. The second information gap was knowledge of how trait changes occur between parent and offspring. Scientists penetrated the genetic code itself embedded in the DNA (deoxyribonucleic acid) molecule. Today we have a general understanding of the three basic processes of evolution:
Species produce like species.
Evolution connects these observations into a meaningful concept of survival of the fittest that only the species that possess superior genetic qualities will survive these harsh, demanding conditions.
The most powerful early interpretation of biological nature came from Aristotle who generalized: purposiveness is an intrinsic quality of all living things. This interpretation of nature is known as “the doctrine of progress.” The need to believe that everything, in the long run, is getting better. Any human act that improves humanity’s genetic standard is moral; any act that preserves inferior qualities is immoral. Evolution’s sublime destiny is to produce superior beings. But the ants have been able to survive, almost unchanged, for eighty million years. Something else is collaborating with evolvement process. Bergson suggested the existence of an élan vital, a dynamic creative power that drives all evolutionary processes. This élan vital is unpredictable and opportunistic, pushing ahead in every species of animal and plant to create greater complexity and higher life-forms.
Three recent insights have emerged in evolutionary theory, all of them revolutionary. The ?rst is the recognition that natural selection is an arms race. All living organisms are trapped in the food chain and must play their given roles as either predators or prey. On both sides increasingly better characteristics are produced at all levels in bodily structure and in the full range of survival skills. Progress of this kind is an elemental fact of evolution. But doesn’t last forever. If the fossil record tells us anything, it reveals that all species eventually lose the battle for life and become extinct. The evolvement of superior qualities continues only as long as a species competes successfully for food, environment, and reproduces.
The second momentous insight into how evolution works is called evolutionary convergence. It has long been known that South America and the Australian continent broke apart several million years ago, and evolutionary development followed different paths. These unrelated creatures look and alike, occupy similar niches, and behave in the same way. Eyes for example, evolved between forty and sixty times independently, in all animals. Apart from anatomy we ?nd similar behavioral patterns everywhere: mechanisms for eating, escaping predators, mating and reproducing, nesting, protecting the young. Evolution is limited due to a certain number of workable body plans.
A third insight into how evolution comes from a biological science called epigenetics, de?ned as the study of inherited characteristics that have nothing to do with genes. We thought, our DNA determines ourselves The chemical molecules of the epigenome tell the genes of the DNA when to express themselves .A human brain cell, for example, contains the same DNA as a heart cell or a muscle cell. The epigenome is sensitive to environmental factors unlike DNA genes. An individual’s epigenetic makeup, to some extent, can be manipulated by change in diet and surroundings. These impacts from environment can be inherited by offspring down through several generations. This means that every living creature, had a hand in the shaping of both its physical body and its behavioral traits.
The critical consequences of discoveries in biochemical evolution create certain conditions. The manipulation of gene codes will lead to a far more fundamental kind of scienti?c activity than before. This knowledge will enable scientists to to produce any desired creatures that he had designed on the drawing board. Ethical considerations raised by the creation and control of life will be complex. We might perceive ourselves as gods—the designers and creators of life. The fact that life will evolve anywhere in the entire universe where friendly conditions exist will eventually become the nucleus of a new worldview .Yet at present the discoveries of biochemical evolution have not made a profound impact. Creating life in a glass tube will be a predictable event in future .Taking over our own evolution—is part of the grand transition that we are now undergoing, the transition from being passively produced organisms to being active controllers of life and destiny.
Questions about revolution’s future remain unresolved. Dr. Harry Overstreet of Harvard University has proposed the idea that man is evolving a new form of consciousness, and that “we have every reason to believe that a further form of our conscious life is already observable among us—a high degree among certain rare individuals, in lesser degree among most of us. Overstreet adds that such appearances of a high order of consciousness are viewed by most of us “as signs either of supernatural power or of psychic disorder. What indeed is evolution’s potential? Are there essential limitations in evolution, or is it unlimited? What suprising life qualities are possible to create and , might become realities?
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