They demonstrated that the monomers required for the macromolecules of life could be produced in the early earth. Later Sydney Fox and others extended Urey and Miller’s work generating polypeptides, carbohydrates, lipids, and other important macromolecules that were biologically active, serving as an energy source for organisms by growing bacteria using the chemicals as a food source. Fox and others determined that the macromolecules generated under the conditions describe above, could, under certain conditions, form “protocells” of various types. These protocells are called microspheres or coacervates. They form primitive but regular arrangements of macromolecules different from the surrounding solution. They have the ability to concentrate organics, creating conditions for chemical reactions that are unique to the protocells compared to the surrounding solution. Some also enlarge and split when they get to a certain size, demonstrating a type of growth and reproduction. These protocells are far from being organisms, but they do show how primordial conditions could have set the stage for life-like structures. RNA’s could have played a role in the ancient earth as both a catalyst and genetic material, roles they still serve. Clay deposits, common in the time period critical for origination of life, can act as catalysts in organic polymerization, and may have played such a role in life’s primordia. The bottom line is that there is experimental evidence to support the transition from an inorganic world to an organic one, in which self propagating aggregates could develop. So can biologists say with confidence how life began? I would have to say no. Are the current hypotheses and theories grounded in natural and testable phenomena as science requires? I would say, yes. So once life was established, how did species originate to produce the incredible diversity of life we see now and in the fossil record. Charles Darwin and the evolution of a theory. In Darwin’s time and before, the church was extremely powerful, and the biblical view of the origin of life permeated science, and culture. In spite of this, individuals began to investigate the physical and biological world to try to find more satisfying answers to their questions–one of these questions was how the diversity of life came to be. The idea that species evolve was not by any means unique to Darwin, many people wittingly or unwittingly contributed to Darwin’s work. Aristotle, an ancient Greek (384-322 BC) Aristotle saw the relationship between organisms, and felt that organisms developed from one another. He even envisioned the concept of mutation–his contributions were noted by Darwin in Origin of Species… Linnaeus (1707-1778) Linnaeus created our system of classifying organisms. By grouping and separating organisms according to similarities and differences the relatedness between organisms became obvious to many. Linnaeus, himself, was a creationist. James Hutton (1726-1797) — Some feel Neanderthals were assimilated into the gene pool of modern humans, that they interbred–there is marginal skeletal evidence. Others feel the Neanderthals were outcompeted by modern humans–fossil evidence not compelling and genetic comparison (DNA extracted from a Neanderthal tooth) did not support interbreeding. What of evolution of modern humans from Homo erectus, there are two prevailing views. The “regional hypothesis” is that modern humans evolved somewhat independently in different parts of the world and were unified by migration. The “out of Africa” hypothesis is that modern humans evolved first in Africa and migrated as had Homo erectus before it. Both genetic and fossil evidence are at this point somewhat ambiguous, although most seem to favor the “out of Africa” hypothesis. More research is needed, and perhaps both hypotheses contributed to modern human evolution. I have only discussed some of the fossils and characteristics. There are ambiguous fossils within the Australopithecus. Homo habilis is very primitive and transitional between Australopithecus and Homo erectus. There are transition fossils between erectus and archaic sapiens, and modern humans. The fossil record shows an abundance of transitions, and clearly establishes important relationships between groups. It also generates almost as many questions as answers however. Extant record can also be used to establish relationships. As we have already discussed the advantage of living organisms is that they can be used to establish genetic links to one another. Their soft tissues can be compared to one another. Just as in the fossil record they show dramatic evidence of relationships, and we see intermediate types, in embryology, reproduction, morphology, genes, etc. Biochemistry likewise speaks volumes about the common ancestry of organisms. All organisms practice glycolysis. All organisms use ATP as the primary source of energy for enzymatic reactions. All organisms are composed of the same basic monomers of amino acids, monosaccharides, lipids, nucleotides, etc. There is a continuum of change when one compares proteins across taxonomic groups (an indirect measure of genetic differences). Homology of reproductive strategies and embryonic development across broad taxonomic groups. Reproductive similarities. Flagellated sperm Reproduction in plants–pollination.
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