Natural selection does not mean nature selects something. It has no such powers (by the way, what is nature?)! Natural selection is merely the sum of all random activities resulting in an outcome. In other words, nature is what is imposed on it!
The first term is random (/ˈrændəm/; as per OALD: done, chosen, etc., without somebody deciding in advance what will happen or without any regular pattern ). Yes, the processes are random.
The next up is activities; what are those? They are DNA replication followed by cell division (our life in one sentence). So, how much copying is happening in our bodies? Humans have about 30 trillion cells (30 followed by 12 zeros); on average, each one divides once a day, which is 30 trillion cell divisions per day. Even if you assume a tiny proportion of error during cell division, you could accumulate a few billion (called mutations) daily.
In simple language, mutations are misspellings of DNA structure while copying. The body corrects most of it, but some may persist. Many of the mutations are neither harmful nor beneficial. So you get away. But, when it happens to the part of DNA that makes up a gene (gene variant), it becomes a serious affair.
Now, let’s come back to natural selection. Some rarer mutations lead to long-lasting consequences (maybe once in a few hundred generations) for an entire species. Say a skin colour change (I will explain that in another blog), a long nose or a pair of wings!
Let’s take the story of tree frogs. Imagine two treefrogs in a society of treefrogs that got mutations that changed their colour – one got grey and the other green. If they lived in a dark wooded area, the accident enabled the grey variety to camouflage away from predators (snakes and birds). If you return after a few years, you will see the area is full of grey tree frogs. Now, change the scene to a green swamp. The genetic lottery is now with the green variant.
The actions were random in both cases, but the outcome was specific.
When Charles Darwin (1809-1882) and Alfred Russel Wallace (1823-1913) came up with the term natural selection, little did they know his grandchildren would give it the opposite meaning.
