For over 150 years – since the time of Charles Darwin – the theory of evolution has been through more scrutiny and rigorous investigation than many other scientific claims. Since that time, the theory of evolution has only gotten more firm and robust. While there are many that, for ideological reasons, want to make it seem like evolution is not widely accepted within the scientific community, this is not actually the case. Across universities, research institutions, and scientific organizations, evolution is not only nearly universally accepted, it is also the basis upon which active, exciting, and important research is being done. Below we have an overview of some of the most notable evidence in support of evolution. The overall goal is to point out the patterns of evolution within nature and help individuals identify other, similar patterns on their own. Doing so will give you the power to, in a sense, test the validity of evolution on your own. Like in a court of law, you have the ability to weigh the evidence in support and against evolution to come to your own conclusion that, in legalese, is “beyond a reasonable doubt”. This list of the “Three Main Pieces of Evidence Supporting Evolution” will read a bit different from other lists. It is not meant to be just a “gotcha!” list of examples that support evolution. The goal is much loftier—to give a complete overview of the most direct evidence in support of evolution. The examples that will be provided are meant to be illustrative in addition to exemplary. Without further ado, the big 3: 1) Species share similarities that are signs of their common ancestry. Think about your family. You and your closest relatives look more alike than you do compared to your cousins. Likewise, you look more like your cousins than you do compared to some distant relative, a stranger, or a person on the other side of the globe. The closer you are related, by-and-large, the more similarities you share. These similarities extend well beyond the surface level and, of course, also reach into genetic and geographic similarities. Sinauer Associates, Inc.(Image source: Sinauer Associates, Inc.) This patterning, like in your family, extends throughout life on Earth. How can we be sure, though, that they aren’t just “common design by a common designer”? It’s the patterning of the similarities that speaks volumes. Similarities (synapomorphies) between species come in nested hierarchies. Meaning, the more similarities you have, the greater in variety and intensity are the similarities shared. Why is this the case? Because the similarities have been inherited from common ancestors and the further back in time any two species shared a common ancestor, the more faded and distant the similarities become. Furthermore, species with a large number of similarities also tend to live near each other—penguin species only live in the Southern Hemisphere, marsupials live almost exclusively in Australia, cacti almost exclusively in the Americas, etc. If evolution is not true, this geographic patterning would make absolutely no sense. Furthermore, these similarities often seem to be completely arbitrary, rather than having some selective advantage. Illustrative example: Insects, though unbelievably diverse, have 6 legs. There are likely several hundred thousand insect species and they all have pretty much the same body plan. Coincidence? I think not! (source)Insects, though unbelievably diverse, have 6 legs. There are likely several hundred thousand insect species and they all have pretty much the same body plan. (Image source: “User:Fir0002”, via Wikimedia Commons) 2) There are progressions of species changing over time. One of the most important discoveries that lead up to Darwin’s theory of evolution was extinct animals found as fossils. Early paleontologists like Charles Lyell and George Cuvier noticed a very simple fact—species that lived in the past are very often drastically, wildly different from anything alive today. Trilobites, dinosaurs, giant sloths, baculites, etc. suggest that life on Earth has changed quite a bit. That would be interesting enough on its own. What makes it more interesting is that the further back one goes, the more different the species appear when compared to today’s. These overarching trends can also be seen on the individual level as lineages can be seen changing over time. How do we know, though, that fossil progressions don’t just represent separate, unrelated species? First, they have similarities that suggest they are related (see above reasoning concerning similarities between species). Secondly, they represent a trend or progression of change. For instance, over time the species go from low expression of a certain trait to intermediate expression to high expression. Lastly, the fossils are dated and organized by direct means (like radiometric dating) or indirect means (like relative dating using unique marker layers, fossils, or other techniques). Example fossils: (source)Human evolution. (source) Fossils aren’t the only way that we can see species changing. We can see it in a laboratory, across geographic distribution as a species spreads, or through artificial selection performed by humans. Examples of species changing in recorded history: All these common vegetables were once wild mustard. (source)All these common vegetables were once wild mustard. (source) 3) Species have traits that are the remnants of past generations. Turn over a manufactured product today and you are likely to see a small sticker or tag that says what country it was made in. Like those tags, species bear the marks of where they came from. These signs of origin might come in the form of repurposed traits, traits that hurt a species chances of surviving or reproducing, or the lack of sensible traits. Put simply, species are flawed and it’s these flaws that clearly tell of their natural origin. Examples: If you didnt know any better, you might think this was a flattened elephant foot. Well, thats not far from the truth since manatees are closely related to elephants. This West Indian manatee (Trichechus manatus) has fingernails on their flippers and hair on their body (visible in this photo). (source)If you didn’t know any better, you might think this was a flattened elephant foot. Well, that’s not far from the truth since manatees are closely related to elephants. The West Indian manatee (Trichechus manatus) has fingernails on its flippers and hair on its body (visible in this photo). (Image source: Fritz Geller-Grimm) Other non-human mammals can produce Vitamin C. They dont need it from their diet. Humans, on the other hand, have had ancestors that have been eating fruit for so long (which is high in vitamin C) that our vitamin C genes is long ago mutated. We do, however, still possess its remnant in pseudogene form. (source)Other non-human mammals can produce Vitamin C. They don’t need it from their diet. Humans, on the other hand, have had ancestors that have been eating fruit for so long (which is high in vitamin C) that our vitamin C genes is long ago mutated. We do, however, still possess its remnant in pseudogene form. (source) What’s so powerful about learning these three reasons that evolution is solid science is that now you have the ability to look at any species and ask yourself these questions: Does this species share similarities with other species that might suggest that they are closely related? Are there progressions of change for this species that we can see in the fossil record, recorded history, or across geography? Does this species have any traits that are the remnants of past generations? Those three simple questions can, if you let them, transform the way you look at the biological realm around you. Go ahead. Ask away. Biology will never look the same.
Posted on: Mon, 02 Dec 2013 01:44:49 +0000
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