I was sitting quietly contemplating the universe on the subway today when I noticed an ad for a local church. And then my mind wandered to so many things, one of which had to do with evolution.
I have no reason to think that evolution did not occur. Mountains of convincing evidence has been presented to me, and logical arguments for evolution are rarely debatable, so I conclude that evolution is a fact. Keep in mind, in science, a fact is something that we observe, and a theory is an explanation of that observation. But why do some people have such a hard time understanding the validity of evolution?
Creationists get upset because they don’t see a dog morph into a turtle right before their eyes. How can evolution be true when we don’t see these things happen right before our very own eyes?
It has to do with numbers.
Pull a strand of hair off of your head. Look at it. See how skinny, thin, and tiny it is? Hair strands are so thin that they almost look 2 dimensional. Now, you can probably picture 10 maybe 20 strands on a table. But you have so many more strands in your own head. You must have thousands, tens of thousands, hundreds of thousands, millions maybe. Your brain is incapable of imagining or picturing all of those strands at once. Yet, they are there. Now try and imagine every strand of hair in New York City. You can’t, its impossibly large. Now imagine every strand in the state, the country, the world… We’re talking about numbers of strands that are so large we can’t even imagine what they would all look like together.
Evolution is the same. The concrete records that we have show us that it takes millions upon millions of years for one species to become another. A million years is an impossible length of time to imagine. People have trouble imagining 12 hours, let alone a million years. But that is what it takes to get from homo erectus to homo sapien.
This is hard to imagine as a whole, but what is beautiful about evolution is that there isn’t any mystery to it. Its fully explainable and logically bullet proof. To this date, no observable or measurable phenomena in nature contradicts evolution, in fact, there isn’t even any convincing hypothesis (by way of ability to be tested) that counters evolution.
So how can we imagine it? You have to scale, big time. Natural selection is the key. It has been observed and considered a truth of life that offspring with a mutation that allows for a higher chance of survival will eventually get propagated through their offspring. For example, finches that are born with longer beaks will have a higher likelihood of survival in places where food sources are deeper in holes. Not every finch that doesn’t have this mutation will die immediately. There maybe only be a few offspring with this mutation in the first generation. But those few will have a much higher likelihood of surviving long enough to procreate and have offspring themselves.
This is nothing new, and not that complicated. Most people are aware of this in nature, and a lot of people don’t argue with it.
But now comes the tricky part. How does that lead to the evolution of man for example. How can something so complicated and wonderful arise from something so simple as a single-celled organisms. Well, just play it out over time.
Imagine natural selection occurring for hundreds upon hundreds of millions of years. Imagine how many generations of species that is, growing exponentially with each generation. Every time a beneficial mutation occurs, it propagated throughout the species until every member of the species has that mutation, then it happens again, and again, and again… suddenly you have a different species of finch. Suddenly, you have a finch with a curved beak, shorter wings, and different color feathers… you have another species. Now, keep in mind that habitats expand, and since we’re talking about hundreds of millions of years, we are talking about MAJOR geological change. Polar bears evolved from a group of grizzly bears that traveled north and got stuck during an ice age. They adapted to their snowy and cold environment, and became a different species of bear.
But how does a fish become a monkey? This very same process actually. But its so hard to imagine, isn’t it? What could a primordial fish chromosome have in common with a modern monkey’s? It turns out that all species have genetic commonalities that are telling of our origins. We have found species of trilobites off of the coast of Australia that predate just about every other species we have a fossil of.Analyzing genetic drift and recombination statistics, we have discovered that chimpanzees, gorillas, and humans diverge at a single point in time, meaning that we all had a common ancestor.
Keep in mind that evolution is complicated and can occur under different circumstances. Sometimes its fully geographic (allopatric) like the polar bear example, sometimes its mostly geographic (peripatric) and sometimes its somewhat geographic (parapatric). It can also have nothing to do with geography. This occurs when you have two different species diverging in the same place, like insects becoming depended on plant hosts. You have to consider reproductive isolation, genetic drift, niche populations and genetic polymorphism.
All of these things are observable and measurable. In fact, they aren’t even disputed.
What is disputed is whether or not any of it has actually been occurring for billions of years. We have fossil evidence that shows us that it has been occurring, and we can deduce logically flawless conclusions based upon current observations of genetic mutation and our fossil record. We are, by the way, incredibly lucky to have fossils at all. It is extremely improbably that a fossil will form for any given species. Conditions must be exactly right for a fossil to form and then be preserved for millions of years. Because of this statistical improbability, the fact that we have so many fossilized species shows us that this planet was home to seemingly endless different species at all stages of evolution. In fact, it has been estimated that 99% of all species that have once lived on this planet, past and present, are already extinct. But I digress.
You know you have a new species when you can no longer reproduce with it. When two groups of a species become isolated from each other because of a mountain formation or what have you, and one species evolves into something more suitable to its new environment, when the two species come back together they are no longer capable of exchanging genes.
Some observed instances of this are insular dwarfism and the Galapagos Finches.
We have actually witnessed speciation in our lifetime (human lifetime i.e. 10,000 years). In 1989, Diane Dodd experimented with the Drosophilia or fruit fly. She took one species of fruit flies and split them into two groups. One group she fed starch-based food to for 8 generations, the other group she fed maltose-based food to for 8 generations. After 8 generations, she discovered that the two groups of fruit flies were no longer able to breed with each other. She created a new species. Evolution, right before our very eyes.
Recent research has found that sometimes parts of chromosomes that switch from one location to another could actually cause a species to split into two different species. This could be explained by the fact that mobile sections of a genome can cause sterility in inter-species hybrids, which would act as a pressure for speculation.
We have discovered that within the gene pool, there is something called an interspersed repetitive DNA sequence. This has been found to function as an isolating mechanism. This actually shows us that species can evolve without needing to be geographically split. These repeats protect genes that are evolving from being overwritten by gene conversion. This occurs because of the creation of non-homologies between DNA sequences. These non-homologies create barriers to gene conversion, which allows nascent genes to evolve without being wiped out by the progenitors of these genes.
As you can see, it would be silly to ignore the extremely high likelihood that all animals have a common ancestry. Everything we observe screams evolution. We have not yet observed anything that contradicts evolution. Nothing. There are no studies that have concluded that genetic drift, natural selection, or speciation probably doesn’t exist.
Alternative ideas of how we got here just aren’t anywhere close to be as sound as evolution. In fact, they are so irrational and without evidence that its a wonder they are even considered by anyone with access to a text book or a scientific journal. Its all laid out for us, easy to reproduce, easy to understand, independently identifiable, and realistic.
Enjoy.
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