The question was asked on Quora and I attempted to answer this question. You can check this here. Interestingly, I was myself looking for an answer to this question until now and when someone else asked the same, I tried to play the role of an expert on the subject matter! However, I wasn’t very much sure about my answer and I tried to convey this in my answer. In fact I posted a link to blog by Jerry Koyne, an expert in this field, who addressed this very question in the said blog.
In any case, I am reposting my answer to the question ‘How can organism evolve without any set of guidance?’ and one other similar question ‘If we evolved form monkeys, why monkeys are still around?’ The answer I posted was written in haste and without proper study. I intend to revise the answer in light of my improved understanding.
Here is my understanding. Suppose you have a computer and a monkey who likes to play with computer’s key board. What are the chances that that monkey will produce a beautiful work of poetry just by randomly hitting the keys? You will say it is almost impossible. BUT NOT ENTIRELY IMPOSSIBLE. In fact, if you give that monkey a billion years to try, the probability to produce a meaningful work would increase. Of course, that moneky would first produce enormous amount of gibberish but you are going to preserve the meaningful work because it has some value. Rest would be thrown away.
Now think about Evolution. Evolution is totally random and unguided. It took millions of years, billions of trials and errors, for Evolution to produce the most basic organism. For example consider mutation. It happens randomly. It can affect any part of DNA. And even if it affects some DNA, it is not necessary that mutated DNA shall be passed to offspring. Even if mutated DNA does pass to offspring, it may not be the case that mutated DNA would result into some alteration in traits because only 2 – 4% of DNA codes for proteins. And even if does alter the traits, those traits may not be beneficial for survival. If that is the case, this may lead to extinction of that species. Only some of them are beneficial.
It is often asked that if we have evolved from apes, why are apes still around. I think the reason is that, as explained above, mutations caused changes in some ape(s), and apparently those changes were beneficial which resulted into survival of new species. Some members of these species underwent some other beneficial mutations. Rest of them didn’t. This cycle goes on and on. This explain how randomness works and why there are so many diversity despite the fact that we do share some common traits with other organism. The more traits we share with any organism, the closer we are in relation. We are closer to apes than cows. We are closer to cows than frogs. We are closer to frogs than fishes. And so on. What does that mean? In the timeline of Evolution, our shared history with apes is more recent phenomenon than cows. Our shared history with Homo neanderthalensis is even more recent phenomenon. Somehow they went extinct but their skeletons have survived to teach us something about Evolution.
In essence, it is about-
1- countless trials & errors and combinations
2- the fact that Evolution has the luxury of having enormous amount of times.
3- natural selection which lets only competent products of ‘trial & error’ survive. You talk about guided evolution because you see the species with beneficial traits. If you could see how many more species didn’t survive because natural selection didn’t favor them, you wouldn’t talk about guided evolution.
Update: Couple of days after I posted above response, I got following comment in response to my answer. It was a good comment and I responded to this comment as well. Read on.
You seem to understand evolution, but then you expressed it badly in one of your paragraphs.
You said: “Evolution is totally random and unguided. It took millions of years, billions of trials and errors, for Evolution to produce the most basic organism.”
That description would suit what you mentioned in the very next sentence, namely “mutation”.
So you could say it like this: “Mutation is totally random and unguided. It took millions of years, billions of accidents and errors, for Evolution to produce the most basic organism.”
I changed two words.
Evolution is not unguided. It is not guided by any sentience or any designer, but rather it is guided by the blind force of natural selection. Whichever version of an organism is best suited to the current environment out-reproduces its neighbors, thereby passing along the genes for whatever made it slightly different from its neighbors.
That does not mean the others die out. They _might_, but nothing requires it. They might linger for a long time as a minor, less successful competitor. And then something changes slightly in the environment, and suddenly the minority has an easier time of living and reproducing, and the variant that had been “winning” for many generations is relegated to the back seat.
Or, a small random change in the genetic makeup of some members might make them just slightly more competitive on the edge of the niche, where the mainstream prefers not to go, or where the mainstream members do not thrive as well, and after a time (and more random mutations), you might have two colonies of similar-but-not-identical organisms living near each other, but each in a very slightly different niche. Maybe one is a colony of bacteria that thrive in a sunny pool in the woods, and the other is a colony that started from the first bunch, and thrives in the same pool, but in the shade of a big rock, where it is slightly cooler.
The guidance is the state of the environment at any given time, and the selective effect the current environment has on slightly different variants of an organism. The changes are random, but the selective pressures that decide whether a mutation will be:
– benign and possibly helpful, or
– benign and neutral, or
– disadvantageous, but not immediately fatal, or
– fatal before reproduction can happen
those pressures are not random. They are characteristics of the environment in which the mutated and non-mutated organisms find themselves.
I thought that your overall answer was good, but that one paragraph didn’t sit well (even though you went on to do better), and the assertion that evolution is unguided didn’t quite fit. We do have to constantly repeat ourselves to creationists and IDers, that the guidance in force does not have a mind or a spook behind it. It’s just a relentless, blind, natural force that does not have any goal or finish in sight. But it works really, really well.
My Response: (to above comment)
I have gone through your reply and read it again and again to find out if there is anything in your response which doesn’t go well with my understanding of evolution (irrespective of what I have written in original reply, I am pretty bad at expressing my thoughts).
I think I don’t disagree with you at all. I mean, there is nothing in your response which is not in line with my own thoughts. Though I think my original reply was merely a short attempt to explain things. Brevity mostly brings with itself all sort of confusion/misconception/oversimplification.
However, when I said evolution is totally random, I meant it in the sense that when an organism changes from A to B (through mutations), it isn’t exactly trying to achieve anything, it doesn’t have any ‘destination’ in its mind and it isn’t exactly trying to be ‘fitter and smarter’ than its previous self. That organism can go from being A to B where being B can be anything from thousands of possibilities. Mutations are random which means transition of A to B is also random.
In this journey from A to B comes the part of Natural Selection play. A can go on to develop into B’ or B” or B”’ and so on. But it is Natural Selection which will decide which version of B to pick up. In other world, the version of B which is going to respond all its surrounding and nature (total sum) in positive manner is going to survive and thrive. Others may not thrive that well. Some may go extinct altogether.
I am no expert in this field. Worse, I haven’t even read any decent book on this topic. As you might have guessed by now, English isn’t my first language so I might have translated my thoughts in a very poor manner. But in any case, I really don’t see any disagreement between your explanation and mine. As I said, I was trying to be concise and in doing so I left out some more explanations and some confusions crept in inadvertently.
In the end, let me be honest, your explanation did help improve my understanding. Thanks a lot for commenting on my reply.
This is the story so far.