Well, I’m not going to simply give you the answer you could get on Wikipedia, although I do highly recommend reading it: Natural selection. I’ll give a little bit of a higher level take on it.

Natural selection is a startlingly simple concept:  “those things that are best able to exist, tend to exist.”

If it sounds rather circular, it is. Some people say it is tautological. But it is quite obviously true.

Now some people may want to say “exist and reproduce” rather than just “exist.”  I don’t think that’s even necessary, if you consider the “thing” to be, for instance, a gene line.

Generally, the term is used to describe biological evolution, but it should be clear that the process happened long before anything we would call “biology” even existed. Chemical processes that could continue, continued, while those that were not able to continue, stopped.  If, by chance, a chemical process changed (by pure chance) into one that was even more stable, it would tend to replace those ones (in the same environment, and using the same raw materials) that were less stable.

At some point billions of years ago on Earth, this process presumably started to gain sophistication at a relatively rapid rate.  “Being stable” required more and more complexity, because there became more and more competitors.  This “arms race” resulted in what we see today — amazingly sophisticated variety of life.


Suppose, you are a moth.
A happy non-melanised moth, camouflaging his way on the lichen covered trees, in pre-industrial england.
You look something like this (in the red circle). The other one is the melanised moth, we’ll get back to him later.

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Natural Selection

Now, enter the industrialization.
Where the humans are really happy, for it will be a better world for them now, you are in great despair!
Why? Because lichens can’t live in pollution. The tree bark is black due to soot now. You can’t camouflage anymore. Predators can easily find you.
You wanna know who is laughing in the corner while you’re being eaten as breakfast?
I’ts this moth.

natural selection of moth

Now, these kinds of moth occupy the area your kind once did.
Your population isn’t exactly wiped out but has decreased substantially.
You still can live peacefully in villages. Your population is still high there.

This, my dear moth, is natural selection.

The organism that is better adapted to the environment and hence, can produce more of its type is selected. His population eventually grows and the other one is wiped out. Over long periods, this can even give rise to speciation i.e. formation of new species.

Want another example? You are too curious for a moth, you know!
Antibiotic-resistant bacteria.

Natural selection is like a non-creative editor. It deletes information; it cannot write information.


Natural selection can also be viewed as a 2 step process:

1. Variation
2. Selection

BOTH steps have to be present.

What all this means is that natural selection is an unintelligent process that gives design.  Natural selection is responsible for the designs we see in organisms:  eyes for seeing, lungs for breathing, the chameleon’s ability to change color, etc.

Let’s get a bit more highbrow:

If under changing conditions of life organic beings present individual differences in almost every part of their structure, and this cannot be disputed; if there be, owing to their geometrical rate of increase, a severe struggle for life at some age, season, or year, and this certainly cannot be disputed; then, considering the infinite complexity of the relations of all organic beings to each other and to their conditions of life, causing an infinite diversity in structure, constitution, and habits, to be advantageous to them, it would be a most extraordinary fact if no variations had ever occurred useful to each being’s own welfare, in the same manner as so many variations have occurred useful to man. But if variations useful to any organic being ever do occur, assuredly individuals thus characterised will have the best chance of being preserved in the struggle for life; and from the strong principle of inheritance, these will tend to produce offspring similarly characterised. This principle of pre-servation, or the survival of the fittest, I have called Natural Selection. It leads to the improvement of each creature in relation to its organic and inorganic conditions of life; and consequently, in most cases, to what must be regarded as an advance in organisation. Nevertheless, low and simple forms will long endure if well fitted for their simple conditions of life. [Origin, 6th edition pp 102-103]

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That’s Darwin’s summary of natural selection.

Just try or think of a simple game between you and your friend.

  1. Take sheets of same size papers and tell him to crumble them haphazardly and tell him to roll them to you on ground to you at a distance.
  2. The clumsy paper balls which reach are selected for next iteration and the rough ones which did not reach you were not selected.
  3. Now you work on it to make it a little more perfect by pressing them and roll it back to your friend.
  4. Repeat this process a million times and each time make the make the paper ball more perfect.

Thats natural selection, different being, nature doesn’t try to perfect anything it just spits out many variations and one that survives according to the current situation is said to be selected for next evolution.

Natural selection is actually a misnomer, nature is not selecting anything, living things are surviving and passing on their genes to the next generation.

If in ten rats in a maze, one are two are successful is reaching the end point,  where there is food, do we say the maze selected the rat?

In a nutshell, Natural selection is survival until reproduction, so it’s kind of both. The more offspring you have, the better you have managed to pass the selection filter. (Note that there are all kinds of interesting details here, like organisms having a stake in the survival of the offspring of their close relatives because they share genes.)

 

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