I posted this to the creationism-evolution debate forum evolutionfairytale.com shortly before being banned for not being a creationist. I thought it worth copying/pasting.
As I said I would I’m making a thread to explain the basic mechanisms of natural selection since some on the creationist side seem to be unfamiliar with it. I would think evolution was absurd too if I only knew what it supposedly can do and not how it can actually do it. I would ask that you please read the entire thing and try to be open-minded and not just mentally argue with it the whole time. Take in the information and think about it.
Like with my other comments I will give some background and history so you know where the idea came from and that it was not, as creationist websites insist, an ideological attack on religion or an attempt to claim there is no god etc – just as the big bang theory which is similarly vilified as anti-god was first proposed by this guy:
A catholic priest and physics teacher at a christian university.
Anyway, here’s how it went.
Darwin started out as a creationist believe it or not. He believed the world was in the order of a few thousand years old and was created as-is. He later abandoned his belief in a young earth (but not a creator), not because of biology or any ideology, but because of a book he read about geology and the evidence of the very old age of things like mountains and other geological formations. He abandoned the strict, literal interpretation of the bible he had in his youth but believed in a creator all his life. The last words of On The Origin Of Species are:
“There is grandeur in this view of life, with its several powers, having been originally breathed into a few forms or into one; and that, whilst this planet has gone cycling on according to the fixed law of gravity, from so simple a beginning endless forms most beautiful and most wonderful have been, and are being, evolved.”
He ended up traveling the world by ship and studying nature, and collected countless specimens and made many sketches and filled several notebooks with observations on his travels. One thing he found on the galopagos islands he could not explain until many years later.
At this point he believed the earth was old but that life had been created in it’s present form. But on the galopagos islands he saw something which seemingly made that impossible. The galopagos islands were spit up by a volcano and as a result there is one big island and lots of smaller islands around it. Darwin observed that on the main island in the center there were many animals and on the outer islands there were similar, but distinct animals that could be consistently and uniquely identified to the island they came from – this seemed to be the case with pretty much every species. At the time darwin figured god could’ve made the animals different on each island for some reason and thought little of it. He captured many specimens to bring back with him. When he returned to the city he asked a bird expert to identify the birds from the different islands and was astonished to be told they were all finches, they were all the same species.
The reason this was confusing is that darwin knew about animal husbandry and knew that animals inherit a blend of their parents’ traits (just like people do), so these finches, unlike the land animals, were not isolated from each other and could fly to the neighboring islands and breed with the other finches, so over even a few hundred or a few thousand years they should not have uniform characteristics on each island, they should all have a blend of different characteristics.
Darwin could not understand why they did not. Years later he formulated an explanation.
He noticed that the finches had distinct traits (for instance some had big, thick beaks like a parrot and others had thin, narrow beaks like a woodpecker) that seemed linked to their diets, because he observed that the wood-pecker like finches ate insects and a wood-pecker like beak would be useful for picking them out of the ground and rotted wood etc, while the ones with thick, parrot-like beaks ate nuts and seeds for which the beaks were useful to crack open, and some ate fruits for which a larger beak would be more useful than a narrow beak.
This gave darwin an idea. He knew that species varied (though he didn’t know about mutations or DNA, that would be discovered later) and that those variations are inherited (think family traits). So he proposed that different variations are inherited at different rates depending on how they effect the survivability of the individual organism. In other words over a hundred or a thousand generations the genes that result in a stronger immune system will be passed on more often than the genes that result in a weaker immune system by merit of the fact that they make their posessors survive at a lower or higher rate. He described this concept as natural selection or survival of the fittest. That nature “selects” the genes for a certain beak because those that possess it starve less often and pass on the genes more frequently over time. This is where we get the concept of gene pools from. It’s also very similar mathematically to how free market capitalism works, unsuccessful business practices tend to disappear and successful ones become common by the very mechanism that they increase or decrease profit.
Species evolve, not individuals. I am not subject to natural selection, but the human race is. Which is why different populations have different resistances to disease, tolerances to things like sugar and alcohol, are at different risks to things like heart disease, diabetes or even cancer and those resistances are hereditary. People whose ancestors drank alcohol for a thousand years have a greater inherited tolerance toward it than people whose ancestors did not, such as native americans which to this day are highly susceptible to alcoholism and alcohol related diseases.
You might say “but how does nature know what changes to make?” The answer is it doesn’t have to. Natural selection happens spontaneously, the useful genes are selected for and the harmful ones are selected against by their intrinsic effects on the individual’s chance of survival and reproduction, no conscious mind is required to understand how or why a gene is harmful. Another way to look at it is this – humans breed animals to be faster (like race horses or greyhounds) or more aggressive like pitbulls and attack dogs or to have stronger senses like bloodhounds. But we have done this for centuries before we even knew what DNA was. If we can breed horses to be faster without having to know why or how they’re faster, why would nature have to know why or how a gene is useful? All that is required is for x genes to be passed on at a lower rate and y genes to be passed on at a higher rate. This can happen because the zebras with the “fast” genes tend to get picked off by the lions the least or it can happen because the winner at the race track gets bred into new generations of racing dogs more often than the losers.
The mechanism is the same. We can design a faster dog without understanding why or how it’s faster, and so can nature.
If you have questions (hopefully in the form of open-minded inquiry, not attacks) please ask them. I will move on though for now.
Darwin talked about the evolution of complex organs like the eye. He said (as it is dishonestly quote-mined by answers in genesis):
“To suppose that the eye with all its inimitable contrivances for adjusting the focus to different distances, for admitting different amounts of light, and for the correction of spherical and chromatic aberration, could have been formed by natural selection, seems, I freely confess, absurd in the highest degree.”
This is a common quote on creationist websites that is presented as “see, darwin said evolution is absurd!”
But he continues:
“Yet reason tells me, that if numerous gradations from a perfect and complex eye to one very imperfect and simple, each grade being useful to its possessor, can be shown to exist; if further, the eye does vary ever so slightly, and the variations be inherited, which is certainly the case; and if any variation or modification in the organ be ever useful to an animal under changing conditions of life, then the difficulty of believing that a perfect and complex eye could be formed by natural selection, though insuperable by our imagination, can hardly be considered real. How a nerve comes to be sensitive to light, hardly concerns us more than how life itself first originated; but I may remark that several facts make me suspect that any sensitive nerve may be rendered sensitive to light, and likewise to those coarser vibrations of the air which produce sound.”
In other words the same mechanism that can produce small changes can, theoretically produce large changes, like the development of entire new organs with complex inter-working parts, but only if the things he listed are true – 1 ) things like eyes vary slightly from person to person, 2 ) the variations are inherited, 3 ) a series of functional intermediate stages can be proposed, and 4 ) those stages are all useful in some environment in nature.
This is four evolutionary predictions – again using the scientific method and saying “if x, y and z are not true my theory is false”.
So lets test them. That eyes vary and that variations are inherited everybody knows is true these days I think. It’s pretty common knowledge that eye scanners are like fingerprint scanners and that everyone’s eyes are unique and that we inherit things like eye color from our parents, so I don’t think I have to demonstrate that (though gilbo12345 will doubtless demand that I do just to be contrary). Now here’s the clincher – a series of functional intermediate stages all of which are useful and fully functional – here’s where the rubber meets the road.
Oh lookie, what do we have here? : )
Not only are all of the stages fully functional, all of them exist in nature.
Now at this point you might pick nits or disagree or argue, but you cannot pretend evolution is not scientific and does not make specific predictions (there are many others I have talked about but are almost all ignored) which, if they were wrong would falsify the theory.
There is lots more to talk about, countless studies and experiments and explanations for all different kinds of organs and traits, the fossil record, you name it. If you want to learn about evolution science (and not the flimsy caricature creationists attack) this is just chapter 1 of the book.