Upstream jagged rocks Downstream smoother, rounder rocks
As we know, rounder, smoother rocks are found downstream in the river. The rounded shape itself is simpler in terms of the shape but is unlikely to occur naturally. To some they may look designed. So how does this happen. Smaller, jagged rocks upstream can be pushed by the water as it flows downstream. The rocks tumble randomly and jagged edges get shaved off due to erosion caused by bumping into other rocks. The collisions are random. In such situations, in the 3D space, and considering the randomness of these collisions, the rounder shape is natural outcome. Few things to take away:
There are jagged rocks upstream. The jagged rocks cannot suddenly become rounder upstream. They have to be rolled downstream to become rounder.
Softer jagged rocks may become rounded quicker.
The rounder form of those rocks are found downstream.
There is no designing agent to make the rocks rounder. It is the outcome of natural laws and physics of rocks and 3D space.
The length of the river has to be long enough without sudden falls for this to work.
If there is a waterfall downstream and rocks tumble over that fall, they may break again and become jagged.
What in the world this has to do with Evolution? you ask. Let me explain...
Evolution is similar. The random mutations in Evolution are like the random jagged edges of the rocks. The environment which kills of the unfit organisms in the population is like the shaving off of the jagged edges. This is called Natural Selection. Upstream is like earlier time. Downstream is like a later time. The long length of the river is like the long timeframes with stable environment over which the process of Evolution works. The waterfall is like sudden changes in the environment, which causes the evolution to take a sudden, different path. The softer rocks are like organisms with shorter generational timespan.
For example, COVID-19 virus is mutating fast (like soft jagged rocks above) and the stronger strains that can defeat the counter measures grow in population. This shows that Evolution does not always takes millions of years, but can be observed at shorter time scales. Also note that COVID-19 variants that infect the host, but do not kill them so that the hosts can move around and spread the infection are obviously the most successful variants. So the success here does not always mean most potent. That is the delta variant. As also can be easily understood, the bigger the population that can get infected, the harder it gets to control the pandemic. That is why we need to mask up and get vaccinated. I do and I have.
When you think of the process of Evolution this way, there is nothing mysterious about it. It is almost commonsensical. There is no active designing agent is needed for Evolution to occur.
I guess it was not a short post after all, but hopefully was sweet. Oh well.