The theory of evolution is well established

Thank you Jellon for taking the time to debate me on this issue. I hope this debate will be stimulating for the both of us!"Nothing in Biology Makes Sense Except in the Light of Evolution" -Theodosius DobzhanskyThe theory of evolution by natural selection is now well established. The original idea was independently arrived at by two scientists, Alfred Russel Wallace and Charles Darwin, the latter presenting it in his famous book On the Origin of Species in 1859. While Charles Darwin already provides compelling arguments for the theory in his book, more than 150 years of research now supports the theory of evolution by natural selection.Briefly, there are two ideas central to the theory of evolution:-that random variations occur within a population of organisms and are inherited across many generations.-that natural selection occurs.Natural selection is the "[d]ifferential survival and reproduction of organisms as a consequence of the characteristics of the environment." [1]Random variations in a population of organisms lead individual organisms to have varying survival and reproduction fitness in a particular environment. A higher reproductive fitness will lead the trait confering the advantage to become more common in a population over many generations. A lower reproductive fitness will lead to the gradual or sudden (if particularly deleterious) phasing out of the trait in a population.Over geological times, with variation in traits and environments between populations, one species can turn into many as it becomes impossible for the members of one sub-population to reproduce with those of another. This process, that naturally follows from the central ideas of the theory of evolution, is called speciation. Speciation implies that many species can arise from an ancestral species. Followed to its logical conclusion, this means that, turning back the clocks of time, each species can be traced back to some ancestral species shared with other species. All species share common descent, another idea Darwin presented in his book.But how does the theory of evolution by natural selection fare when it comes to the evidence? Here I will invoke the concept of consilience (The "[a]greement between the approaches to a topic of different academic subjects, especially science and the humanities" [2]). I will show that different sources of evidence all converge conclusively towards the theory of evolution.Evidence from geneticsCharles Darwin's theory of evolution largely predates the field of genetics, yet the findings of genetics fit particularly well with the theory of evolution.The first thing to notice is that the field of genetics gives random variation in organisms a support (the genetic code [encoded by DNA/RNA molecule]) and a cause (random mutation). Mutation is "[a] change in the sequence of one or more nucleotides in DNA. [...] In some cases mutations result in the organism possessing these altered traits to have a greater or lesser chance of surviving and reproducing in a given environment than other members of its species. " [1]The genetic code of an organism, along with the mutations it has aquired are passed on to offspring through reproduction. Genetics therefore offers a way whereby evolution can take place.The theory of evolution implies that all living species share a common ancestor. This is patent in the universality of the genetic code. Every living species has a genetic code composed of a series of 4 repeated nucleotide bases. Because of this universality, it is possible to take certain genes from one species and express them in another as illustrated by the GloFish, a zebrafish which has been genetically engineered to express the fluorescence protein of a jellyfish, leading to fish that glow.[3]If the theory of evolution is correct, common ancestry between two species should be reflected in the genetic code. The phenotypical traits displayed by various species can give us a fairly good indication of how related two species are in comparison to other species. If the theory of evolution is correct and the mechanism underlying it is supported by genetics, we should observe species sharing a recent common ancestor share more DNA sequence than either with species with a more distant common ancestor. Scientists did not wait for the sequencing of genomes (a fairly recent feat. that occured around the turn of the century) to investigate this. DNA-DNA hybridisation has been used to determine how similar the DNA of two species are by combining the DNA strand of one species, to the complement strand of another species. (4) How well these strands fit depends on sequence similarity. This technique confirmed much of our intuitions and lead to further classification. Crucially it showed that Man and Chimpanzees share ~98% of their genetic code, evidence of recent (in geological time) speciation eventually leading to both those species. Whole-genome sequencing confirms this similarity, showing that the genetic makeup of bonobos is also extremely similar. [5] Species as different as the wild banana and Humans betray their ancient, but existent, common ancestry through the ~50% of their respective genetic codes they share. [6]The field of genetics has a lot to offer in the way of confirming the theory of evolution, but I will move on to other forms of evidence.The fossil RecordThe fossil record is one of the older forms of evidence for the theory of evolution and unlike genetics, some of it predates the theory of evolution and helped formulate the theory in the first place.Over many centuries, the fossil record has introduced us to many species that no longer exist in our modern world. The fossil record is testament to the change that has occured in organisms over billions of year. As we travel through the layers representing different ages of the Earth, we encounter fossils that tell the story of evolution. Importantly, the fossil record shows species with increasingly more complex structures consistent with the accumulation of advantageous variations over time. [7]The fossil record is full of transitional fossils. UC Berkeley's website defines transitional fossils as follows:"Fossils [...] that show the intermediate states between an ancestral form and that of its descendants are referred to as transitional forms. There are numerous examples of transitional forms in the fossil record, providing an abundance of evidence for change over time." [8]Transitional fossils thus show us gradual change over time, for life as a whole, but also for specific species or a set of species. The relationship between species (the subject of the field of phylogenetics) patent in transitional fossils allows us to draw up a tree of life. This tree is consistent with a number of traits inherited by all species of a particular group. The common ancestor to all mammals has traits that all mammals have (e.g. mammary glands) and that no other separate branch has developed. We can observe this at different levels.The meeting of genetics and the fossil record is ripe with consilience. To name just one, the tree of life suggested by the fossil record fits with the tree of life determined through genome comparison and DNA-DNA hybrid studies. Two different fields come to the same overall conclusion, which we can link to traits in species. We can also look at the genome of different species to discover regions conserved in groups of species. These conserved regions must have appeared in a common ancestor and will thus not be found on other branches. They are inherited.Evidence from geographic distributionWe know from geological sciences that the different continental plates once came together as the great supercontinent Pangea but have since drifted apart. The geographical separation of species can be gleaned in the fossil record, with the same fossils being found on two different continents at a time when continents were one, but different fossils being found thereafter.Consistent with this observation, we find quite different species on different continents. Furthermore, we find species that are endemic ("(Of a plant or animal) native or restricted to a certain place" [9]) to a certain island. Australia for example has diverse species termed Marsupials, a groupping found only in Australia because of its geographical isolation. Madagascar present the same characteristic with species such as lemurs found only there.The ancestors to all of those species following continental drift are geographically consistent. The recent fossil ancestors of an African lion will not be found in South America for example.The evidence for the theory of evolution of course does not end here. Each of the sections I have presented have more evidence to bring to the table. Other forms of evidence I have not had the opportunity to present. It is important to keep in mind that evidence for the theory of evolution by natural selection has been piling up for a century and a half.It is also important to stress that any of these pieces of evidence on its own can make a resounding case for the theory of evolution. That we have so many fields in agreement that we can bring together through consilience only consolidates this already established theory.The theory of Evolution is well established.References[1] http://www.nas.edu......[2] http://www.oxforddictionaries.com......[3] http://www.nature.com......[4] http://evolution.berkeley.edu......[5] http://news.sciencemag.org......[6] http://www.nhm.ac.uk......[7] http://www.dmp.wa.gov.au......[8] http://evolution.berkeley.edu......[9] http://www.oxforddictionaries.com......[10] http://www.oxforddictionaries.com......