The challenge, for all and sundry but especially for “Darwin doubters”, should you wish to take it, is to submit a one-paragraph summary of the theory of evolution. The idea is to see if you understand it well enough to fairly summarize the theory so that you pass as a proponent of evolution. We also need some examples from proponents to test the null hypothesis!
To ensure anonymity, please submit your paragraph by private message to me or another admin and we will add it in edit. (Or email it to me at firstname.lastname@example.org if you prefer.)
Speculation and divination are enouraged in the comments!
ETA some degarbling!
The Theory of Evolution (hereafter referred to as just evolution is generally credited to Charles Darwin. In his book, Origin of the Species, he described his observations regarding finches in the Galapagos Islands. He noticed that living organisms, when they reproduce, are reproduced with slight modifications. In essence that organisms descend with modification. The first crucial part of evolution is this basic idea. What we now refer to as descent with modification. Gradually, over much time, continual modifications are made to generations of descendants, and after much time, the descendants may be quite different in function and appearance than their ancestors. The first part of this theory was established prior to our current knowledge of DNA and genetics. After the discovery of DNA, and as we learned about how genes are copied, evolution was confirmed because we learned in fact that genetic s are not copied perfectly. Instead there are slight changes, we call random mutations. We now know that Charles Darwin’s ideas about descent with modification were correct and more precisely we know that those modifications happen through random mutation. The second crucial part of evolution is the idea of natural selection. When random mutations happen, they are mostly nonsignificant and have no bearing on an organisms ability to survive in their environmental niche. However, sometimes the random mutations are negative and those specimens die out quickly and don’t reproduce. For instance, albino rabbits are more easily seen and captured by the foxes than are rabbits that are brown. In other cases though, the random mutations result in positive changes to an organism in their given environmental context. These mutations allow the organisms to be more fit for their context and thus they are more successful at reproducing. Gradually over time, natural selection weeds out the less adapted versions in favor of the newer adaptations. An example of this can be seen in the black and white moth scenario in the UK. Together, Random mutation and natural selection along with ‘deep time’ make up the heart of the modern synthesis of evolution. The theory continues to readjust slightly over time with additional research. For example, recently, a minority of scientists (Kimura, et al) have emphasized simple descent with modification as the primary driver of evolution, though not totally discounting natural selection. In essence a neutral drift of the species mostly.Â There are other slight variations with the models, for instance Stephen J Gould famously proposed a punctuated equilibrium model as an alternative to the ‘gradualist’ model. In neither of the mentioned cases though was evolution rejected. Instead, proposed variations to the theory were given. There are generally some very convincing evidences for evolution. The fossil record and its various layers support the theory of evolution. The age of the universe supports evolution. Vestigial features such as the hair of the human arm standing on end when we are scared or cold provide compelling examples. Junk DNA provides powerful evidence of evolution. And the close relationship, DNA wise of chimps and humans provide strong evidence for evolution. The origin of life, abiogenesis, is generally considered outside the conversation of evolution and not strictly speaking part of evolutionary theory. Evolution gives a clear model for explaining the diversity and similarity of living things across the earth. Contrary to some opinions evolution doesn’t necessarily make any statement about theism or atheism.
The theory of evolution is that biological organisms develop from one physical state to a different physical state by incremental steps through selection of successfully reproducing members of a population. Those successfully reproducing being due to mutations affecting members of a population and those members gaining a advantage in a environment of the moment. The mutations being the important element for biological change may mean also that selection is not needed in a population and so new populations may simply occur upon mutations alone. The evidence for the theory is from a system of close attributes in organisms demonstrated by a tree formation. These attributes are used to show a spectrum of biological relationship and so common descent to be demonstrated. Genetics and the fossil record are also essential evidences and based on attributes showing a spectrum of divergence. Other evidences based on comparison of attributes also are included. Starting from a hypothesis the accumulation of evidence and general explanatory weight has turned the hypothesis into a theory in biology. Within the evolutionary biology community there are important or notable differences in ideas on aspects of evolution however the core concept is a foundation.
Whether it is a court case or science, the capabilities and limits of causes of specific effects are crucial to deciding whether or not there is good reason to doubt the alleged cause or causes. Evolutionary theory lives or dies on the evidence of the specific effects caused by its capabilities and limits, as should any other claimed cause of life and its diversity. In simple form, evolution is caused by reproduction, which passes inherited information from parent to child, or from single cell to daughter cells, with considerable fidelity, but also with changes in that information called mutations. Detrimental mutations tend to be weeded out by natural selection, while natural selection tends to retain beneficial mutations, and over many generations intersecting and additive beneficial mutations may lead to new features, such as flight. Much more happens in evolution, like neutral or near-neutral mutations, bottlenecks, and genetic isolation (or not), but natural selection tending to eliminate what does not lead to reproductive success and favoring what facilitates reproductive success is usually thought to be the most important process. With these evolutionary processes in place there is considerable scope for impressive change over long periods of time, but there are also important limitations to it that mark evolved life with the evidence for evolution. Notably, while there is some genetic flow between reproductively separated lineages, especially in prokaryotes, polygenic traits are quite unlikely to be transferred to, for instance, vertebrates. Vertical transmission of DNA information predominates in most eukaryotes, and is quite evident in prokaryotes as well. The relative lack of portability of information across separate lineages shows up in the vertically derivative genomes of vertebrates in general, which is seen as nested hierarchies in taxonomy. The limitations of evolutionary processes apparently produce the patterns of life. An interesting example is to be found in the three types of flying vertebrates, bats, pterosaurs, and birds, which all share obvious yet fairly distant homologies, but whose flight adaptations are entirely uninformed by each other at all, apparently due to the fact that all three groups had diverged before each group evolved flight. The same evolutionary limits mean that birds do not have the fine auditory bones that evolved in mammals, while mammals do not have the improvements in eyesight that evolved in birds, such as the pecten (nor do mammals have the more efficient lungs of birds). Vestigial organs are a peculiar case of information retained that is no longer useful for a specific purpose (but may have other current uses), such as the tiny bones of the human coccyx that apparently evolved from tail vertebrae. The general trend of the fossil record is also what would be predicted by evolutionary theory, with amphibians needing dampness evolving first from fishes, then reptiles evolving for drier climates, while mammals and dinosaurs (including birds) evolved insulation for colder areas (among many other changes). “Transitional” forms like Archaeopteryx reveal the incomplete and inefficient adaptations expected from evolutionary processes that are mostly incapable of all but incremental change. The specific patterns and evolutionary developments visible in present life and in the fossil record point with consilience to a specific set of processes that we see happening today, the evolutionary processes of inheriting DNA information with some variations in that DNA, along with natural selection tending to retain reproductively helpful changes, while tending to eliminate reproductively harmful changes.
The theory of evolution holds that there has been, and continues to be, change in form via change in the genetic makeup of organisms during the succession of a lineage – summarised as ‘descent with modification’. The primary source of these modifications is provided by mutation, arising from copy and repair errors and DNA damage, but also with significant contributions from recombination, gene transfer and transposition. Many changes are lost, but some become fixed, an inevitable consequence of the blind resampling process that is involved in a succession of generations in populations of finite size. Where a change is neutral, it may become fixed in a population through genetic drift alone. Where non-neutral, both drift and selection are involved. The change affects its own survival in the population, by influencing the rate at which it is passed on to descendants, when compared to the neutral expectation. Detrimental changes are more likely to be lost, and this will occur more rapidly on the average than neutral ones. Conversely, beneficial changes are more likely to become fixed, and again this is likely to happen more rapidly than the neutral case. These latter processes constitute the modern version of Darwin’s principle of Natural Selection, which lacked a sound genetic basis when first proposed, but nonetheless articulated the basic requirements of variation and excess of production over carrying capacity.
Within sexual populations, interbreeding tends to maintain an entire population in step, but where gene flow between such populations is reduced or eliminated, divergence is inevitable, leading to the phenomenon, at a moment in time, of multiple fixed and distinct types derived from the original single population. With increasing time, ongoing divergence leads to broader and broader taxonomic classifications with greater and greater difference between them, but all tracing back to simple population-level splits at varying depths in the time series.