Is evolution a fact or a theory? What observations prove that evolution is taking place right now? Those are two big questions often posed by the vast majority of people who (at least in America) still desperately cling to the notion that God created the universe and all in it in a matter of just 6 days. Right now, the battle of evolution vs. creationism is being joined again as Tennessee Governor Bill Haslam is poised to sign a bill that would protect teachers who criticize evolution/promote creationism in the classroom.
So, all heated opinions aside, what is the evidence that has helped turn evolution from Charles Darwin's personal hypothesis into a virtually unassailable scientific theory that, in all common sense, should have long since been accepted by the vast majority of the population?
First of all the theory itself. According to Darwin, all current life forms evolved from simpler ones. The agent for change: natural selection, which is, at the most basic level, the idea that, due to genetic differences, certain individuals of a species gain a biological advantage that aids in survival. Result: those individuals with the given edge, whatever it may be, are more likely to survive and reproduce than individuals without the one key difference. In time, those individuals with the advantage will keep surviving and reproducing while the ones without the advantage will die off and reproduce less and less as time progresses. In time, a new species will evolve and the old one will become rare, possibly extinct.
An accelerated illustration of evolution is the process wherein humans selectively breed animals for desired characteristics. This is called artificial selection because the agent of change is deliberately imposed on the animal from the outside by humans.
Natural selection, where certain genetic errors actually prove advantageous to survival, works on a much slower time scale measured in the tens of thousands, millions, and billions of years. In time, this process that started with inanimate matter spontaneously assembling itself, an idea that has been proven by experiment, is what has taken life on Earth from single-celled life forms like bacteria algae into the entirety of what we see around us today, things such as flowers, trees, birds, fish, cats, dogs, and, of course, humans.
Now, for evolution deniers, one of the biggest problems with the idea is that of the slow time scale, wherein natural selection works at a pace too slow to witness during the human lifetime. However, thanks to rapid advances in technology, that notion can easily be disproved.
In one wants to see evolution by natural selection at work, one needs to study the smallest creatures on earth, the single-celled organisms that are, in fact, direct descendants of humanity's (and everything else's) most distant ancestors. It is a common piece of knowledge that certain bacteria are developing antibiotic-resistant strains. While this is a troubling, some would say frightening discovery for the general public, it is ideal ammunition to be used against those who continue to deny the theory of evolution. For anyone who's willing to consider evolution over longer spans of time, there are many observations supporting the idea that life is continually evolving from simpler into more complex forms, such as the fossil record, genetic similarity between all life forms at the DNA level, and the geographic distribution of related species.
In science, there are no absolute truths and there is just one commandment: respect the facts. Yes, evolution is considered a theory, which is far different from a hypothesis. Yes, while it will never be 100% proven that evolution by natural selection is the mechanism that created all life on Earth as we know it, the evidence in favor of the theory is very overwhelming to say the least. Yes, while evolution will always remain a theory, it is a theory with one of the firmest foundations in science, one that we owe it to our children to have in the classroom.
For more info:
Scientific answers to creationist arguments
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