Some of you may notice a lot of overlap between this page and the Useful Notes -- Evolution page over at TVTropes. That's because I wrote a significant chunk of that, and I make no bones about it. Other people have also contributed to it, not least they made it not look like ass. They also tidied up the verbiage and corrected quite a bit of my biology. Anyway, on to destroying some myths!
Evolution Has No Goal
Evolution is a stochastic (non-deterministic) process. It's not building toward anything in particular; hell, it's not building toward anything at all; hell, it's barely even building. Evolution moves around randomly, sampling the landscape of potential forms and behaviors. It fills every niche. In so doing, it creates new niches, then it fills them, creating new niches to fill! Leave it to a nineteenth century poet to say it:
Great fleas have little fleas upon their backs to bite ’em,
And little fleas have lesser fleas, and so ad infinitum.
And the great fleas themselves, in turn, have greater fleas to go on;
While these again have greater still, and greater still, and so on.
De Morgan: A Budget of Paradoxes, p. 3771
Evolution is sort of like a gas; it expands to fill the space it's in. But it's also simultaneously creating that space. It's a weird, squirmy, umpty-dimensional gas. Wibbly-wobbly, timey-wimey. But it doesn't have a goal. It doesn't pick winners.
The most tragic consequence of this myth is what it did with the notion of the superior race, which was around long before Darwin developed his theory. The Nazis were the most famous purveyors of this myth, but it was widespread among many groups in many nations until the Nazis demonstrated how utterly horrific it is when taken to its natural conclusion. This myth, and its natural end, are both used by opponents of evolution as an argument against it, but evolution doesn't predict this.
A human, a tree, a sea slug, and an E. Coli bacterium are all highly evolved organisms, flourishing in their environments and striving to pass on their genes. None is superior to the others, none more highly evolved. A cheetah is particularly well adapted to running down fast prey, but it will never outfight a bear, which will never be as deft with its paws as a raccoon, who can't swim with the fishes, who don't know how to do math. We are each of us what we are, with nearly the same 3.5 billion years of evolutionary history behind us. And a tree won't have nukes, anger and lower back problems2.
Evolution: More than Mere Chance
Evolution is an unguided, stochastic process with randomness at its heart, but randomness isn't the only thing their is. Natural selection is an incredibly powerful tool that immediately weeds out negative changes and strongly favors positive.
Imagine 1000 people flipping coins. If they flip every five seconds, how long before they come up all heads? On average, 1,697,702,940,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000 years. That's 10^284 times longer than the universe has been around.
Now, imagine that they all flip and keep the heads. Everyone with tails flips again, and they keep the heads. Anyone who has tails flips a third time, and so one. How long before we have all heads? 500 + 250 + 125 + 62 + 32 + 15 + 8 + 4 + 2 + 1 + 1 = 1000 heads in 11 flips, on average, for a total of 55 seconds. Flipping randomly hoping to get a particular outcome is unrealistic, but once you throw in the power of selection, you take away the sting.
Whether life on our planet is as dramatic as my coin toss example depends on the power of your imagination.
Evolution Promises Very Little
Evolution doesn't promise us the best of all possible worlds. It promises us the bare minimum to get where we are right now. That's why we have lower back problems. And wisdom teeth that get impacted. And a tiny piece of intestine that likes to crawl up its own ass and die. And then there's the pregnancy thing. And the pelvis thing. And our knees. And we're blind and deaf. And our children are completely fucking helpless for about a decade and a half. And have I mentioned that we can't run very fast? And we're no good in the cold. Or the hot. Or the water. And man alive the desert will kill us so fast.
And that's just what's wrong with human beings. Evolution isn't magic. It'll find solutions for all of our problems, but it'll take a few thousand generations, and it'll find new problems along the way.
Evolution is About How Life Changes
It isn't how life began. The origin of life is called abiogenesis. ('a' - not, 'bio' - life, 'genesis' beginning. 'abiogenesis' - how life came from non-life). Evolution is about how life, once it's here, has developed and changed. Descent with modification and natural selection is the theory that explains the observed process of change in life already extant.
Abiogenesis is a hella interesting field that lies in the borderland between geology, chemistry, and biology. So far we know that it took at most about half a billion years for life to appear on Earth, however it formed, because we have fossils of bacteria nearly four billion years old. We can know something about the conditions, and geology and chemistry and physics are all working together to piece together those conditions and give us a clearer picture. Then biochem steps in and works out how you get from those to how life can appear. It's a wonderfully fascinating endeavor.
But it's not evolution.
I'll be honest; we might not ever know exactly how life evolved on Earth. If we're phenomenally lucky, then perhaps we'll get to observe it happening on another planet, or maybe we'll make incredible breakthroughs in theoretical chemistry and physics and develop a fantastic model of the early Earth. I don't know; ignorance actually is an acceptable position to take in science. "I don't know" is always the starting position, and a possible finish line. It's never a satisfying position, but it's acceptable in the face of little or no evidence.
But abiogenesis and the current state of that field of study have no bearing on evolution. Evolution is so well established that trying to overturn it is like trying to overturn gravity. When I say we have tons of evidence for it, I mean literal tons. We're talking about actual rocks here.
We'll cover more myths in part II.
1 - The line originally appeared in a poem by Jonathan Swift, who was mocking the idea of self-similarity in fractals. What I quoted is from a mathemetician later in the century who was also discussing fractal self-similarity. But it works.
2 - Those three lines I lifted right from the TVTropes page. I wrote the original, but it's been edited since, and I have to give props to user memememememe for fleshing it out.