Evidence_for_Evolution

Evolution: The Facts Behind the Theory The theory of evolution is not, as is commonly assumed, equivalent to Darwinism; it is not a process, nor something to believe in. Evolution is not something that only happened in the past, it does not deny the theories of Creationism or Intelligent Design, but it is an alternative explanation. The theory of evolution is an interrelated set of now well-confirmed hypotheses, and theories, including descent with modification, natural selection, genetic drift, and genetics as the mechanisms behind the evolutionary process itself. The mechanism for how evolution happens has been largely explained by natural selection. Natural selection is observed constantly, and its role as the main driving force of evolution (the Theory of Evolution by Natural Selection, essentially as Charles Darwin proposed) has been observed, tested and challenged many times and in many ways, and has survived largely intact. There are also many independent lines of evidence that are consistent with natural selection as the main mechanism of evolution. There is no observed evidence against this as a working process for evolution. Efforts by some to point out "evidence against evolution" always turn out, under critical examination, to be without merit. The Theory of Evolution by Natural Selection (or, more accurately, the Theory of Natural Selection), therefore, holds the high status of near certainty: it is a scientific fact. By extension, as this process of speciation proceeds with time, an increasing numbers of species appear, becoming increasingly different. The pattern of natural selection looks like a branching tree; all the species we see today are like the growing tips of that tree, close clusters of tips have most recently branched (evolved); more distant tips can be traced to much lower (earlier) branches in the tree. The recognition of this pattern of change in life forms over time was developed from many observations. It has even been directly observed in some species, and inferred in many others from clear independent evidence mainly in comparative anatomy, embryology, paleontology, geology, genetics and biogeography. Although there are some curious examples of evolution, there are no empirical observations of life, living or extinct, that evolution cannot explain, and there is absolutely no evidence to disprove evolution. One of the strongest arguments to support evolution is the comparison of anatomies of different species, consisting of homologous structures, analogous structures, and vestigial structures. Homologous structures are characteristics, which are shared by related species because they have been inherited in some form or fashion from a common ancestor. For example, the bones on the front fins of a whale are homologous to the bones in a human arm and both are homologous to the bones in a chimpanzee arm. The bones in all of these different body parts on different animals are fundamentally the same, but their sizes are different and they serve slightly different functions in the animals where they are found. The presence of homologous structures can also be defined as divergent evolution: while the structures are generally the same between a species and the common ancestor, but the functions of the structures have changed throughout the course of evolution. However, not all similar structures are homologous, for example, some biological characteristics are analogous, which means that they serve the same function in different species but they evolved independently rather than from the same structures in a common ancestor. An example of an analogous structure would be the wings on butterflies, bats, and birds. While these wings serve the same purpose (to fly), their structures and make-up are completely different. It can be confirmed that beneficial traits, will be “naturally selected” for, but will be produced in many different ways. This process is called Convergent evolution, where dissimilar animals will evolve and develop structures to serve the same beneficial purpose. Some organisms have structures or organs that seem to serve no useful function. For example, humans have a tailbone at the end of the spine that is of no apparent use. Some snakes have tiny pelvic bones and limb bones, and some “cave-dwelling salamanders have eyes even though members of the species are completely blind.” (“Evidence for Evolution” SparkNotes) Such seemingly functionless parts are called vestigial organs or structures. Vestigial organs are often homologous to organs that are useful in other species. The vestigial tailbone in humans is homologous to the functional tail of other primates. Thus, vestigial structures can be viewed as evidence for evolution: organisms having vestigial structures most likely share a common ancestry with organisms in which the homologous structure is functional. Embryology, as the name suggests, is the study and recognition of organisms in an embryonic state. There exist many similarities between different species whilst in n embryonic stage, and though embryology, one identifies and analyzes the similarities and differences. Even though some organisms appear to be completely different in anatomy, homologous structures not present in an adult organism often appear in some stage of embryonic development. In this way, the embryo serves as a microcosm for evolution, passing through many of the stages of evolution to produce the current state of the organism. Species that bear little resemblance in their adult form may have strikingly similar embryonic stages. For example, in humans, the embryo passes through a stage in which it has gill structures like those of the fish from which all terrestrial animals evolved. For a large portion of its development the human embryo also possesses a tail, much like those of humans’ close primate relatives. Therefore, proving that there must have been a common ancestor for which all life evolved from, and certain structures and organs have been deemed unnecessary over time. This final section is perhaps the most straightforward and certainly one of the most persuasive stand-alone bits of evidence that supports evolution. Based on Descent with Modification (Evolution), if one species is the descendent of another, then there must have been some geographical continuity from where the parent species is found to where the child species is found—they had to be able to get there. Of course, if this geographical continuity was broken at some point in the past, then there would be predictable adaptation—but only if Descent with Modification is true. Australia is a fine example of how biogeography supports evolution. Deeper layers of the fossil record show that marsupial mammals (pouched mammals like the kangaroo) were more common than placental mammals (mammals like humans that gestate their young inside their bodies with the use of a placenta). During this time, some parts of the world were populated only by marsupial mammals, including the landmass that would eventually become Australia. Shallower (more recent) layers of the fossil record show that placental mammals had displaced the marsupials over much of the earth. But what if a barrier appeared before the expanding placentals could invade a particular area that had been occupied only by marsupials' For example, what if a peninsula that had been occupied only by marsupials, became an island before the new placentals migrated there' Well, Descent with Modification would predict that the isolated marsupials might not only survive, but they would evolve and develop many analogies, or homologous structures to placentals, and only in one place: their isolated island. There is an incredible amount of evidence for evolution without even looking at a single fossil. Our modern wealth of knowledge about anatomy, embryology, biochemistry and biogeography provides ample evidence for evolution on its own. But the fossil record does have a unique characteristic that none of the other evidence does: it is the only actual glimpse into the past where common descent is proposed to have taken place. As such it provides a valuable – or perhaps invaluable – piece of evidence to support common descent. The history of life, as represented by the fossil record, generally supports the theory of evolution without considering other evidence. If the fossil record is observed, a succession of organisms that is suggestive of incremental development is found. Very simple organisms are found at first, in earlier levels of strata, and then new, more complex organisms appearing over time. The characteristics of newer organisms frequently appear to be modified forms of characteristics of older organisms. Thus, this succession of life forms (from simpler to more complex, showing relationships between new life forms and those that preceded them) is suggestive of evolution. There is an overwhelming amount of evidence to support evolution, much more then what is described in this paper. And it is assumed, that only the most obvious and easiest topics to understand were addressed. So, when one talks about highly technical details regarding some particular measurement or method, remember that one particular measurement or one particular method is not why scientists believe that evolution is true. The critic of Evolution has to show, not how a measurement or method may be wrong, but, how all of the thousands of different measurements using many different independent methods came up with the same wrong answer. It is, in fact, likely that errors will be made, precisely for the reasons creationists give: these techniques are not perfect. This is precisely why science doesn't consider any theory based on a few data points, but only when there are a many data points and a good deal of independent collaboration. Keep in mind that errors and unexpected results are reported with the rest of the data. This is how science accounts for the errors of measurements, and the imperfections of individual scientists. So it is with evolution. The creationist has to ask: How did all the possible errors that could happen, did happen, and how they all conspired together so that as a group they would have absolute agreement around the same incorrect conclusion' That is what is meant by independent confirmation; that is what is meant when a theory is supported by the evidence; and that is what the critic needs to explain. Indeed, his or her alternative theory must not only explain the same phenomena, but must account for the errors in the opposed, and not simply point to the obvious fact that mistakes can be made, or that some questions remain, as they do in every field of science. Evolution is a theory, and much like the theory of gravity or the atomic theory, it explains the facts and evidence provided. Evolution is widely accepted throughout the scientific community. The theory of evolution, and all functions associated with it, is the only scientific theory that explains the mystery of how life exists as it is today. “While most of biology attempts to describe what the natural world is like, evolution explains how and why it became that way. The forces that drive changes in species are vital to an understanding of life itself.” (David Quamen 1) If one does not agree with the theory of evolution, so be it, it is just a theory, but keeping in mind: it is a theory that has enormous amounts of supporting evidence, and is about as close to “fact” as a theory can get. Any other possible explanation is unnecessary. “Nothing in Biology makes sense, except in the light of evolution.” -Theodosius Dobzhansky