Natural Selection

Natural selection is one of several key concepts within the theory of evolution. To explain exactly what natural selection is and why it's so important we need two other evolutionary concepts: Descent with Modification and the daring idea of Common Descent. 

Descent with Modification is the fact that when parents have children, those children often look and behave slightly different than their parents, and slightly different than each other. They descend from their parents with modifications. 

The differences found in offspring are due to random genetic mutations.

Common Descent is the idea that all life on Earth is related, that we all descended from a common ancestor. Through the gradual process of descent with modification over many generations, a single species is thought to have given rise to all the life we see today. The common descent of all life on earth is not a directly observable fact. We have no way of going back in time to watch it happen.

Instead, Common Descent is a conclusion based on a collection of observable facts. Facts found independently in the study of fossils, genetics, comparative anatomy, mathematics, biochemistry and species distribution. Because the evidence for common descent is so overwhelming, the concept has been around since ancient times.

However, it was rejected by many philosophers and scientists for one  main reason: You cannot get order from random chaos alone. Descent with Modification simply produces random variation.

All through history  no one could explain how complex life arose from simple life through just random variation, until I discovered Natural Selection. At the start of his career I traveled the world by ship, collecting and documenting nature.

I noticed that islands contain species of plants and animals unique to those islands and can't be found any place else on earth, but they often look and behave similar to creatures found on nearby continents and islands.

Tortoises on the Galapagos islands can be distinguished from those of Africa, meanwhile, (with the exception of size) they're almost identical to a species found nearby in South America. I believed these similarities could best be explained through Common Descent. Long ago a tortoise from the mainland may have drifted to the islands, possibly on a raft of storm debris, and once arriving, laid her eggs.

Random changes caused by Descent with Modification over thousands and thousands years, eventually transformed the island creatures and the mainland creatures so much, that they could no longer be considered the same species. This idea made good sense to me except for one thing: the island creatures I found were not just randomly different from their cousins, they were specially adapted for life in their new territories. 

The Galapagos is a collection islands, many of which are home to tortoises. The larger islands have lots of grass and vegetation. Tortoises there grow extra heavy and have dome like shells. Some of the smaller islands have very little grass, forcing the tortoises to feed on island cactus.

The best cactus pads grow on the tops of these plants.

Fortunately, tortoises on these islands are equipped with necessary modifications to allow them to reach that far. It's almost as if these island creatures have been perfectly sculpted to survive within their environments. 

How did this sculpting take place? Random Descent with modification alone could never do something like this. I drew upon my knowledge of selective breeding to answer this question. For thousands of years, farmers have been taking wild plants and animals, and through the process of selective breeding, have sculpted the original wild forms into new domestic forms, much better suited for human use. The process is very slow but simple.

 If a single plant produces a hundred seeds, most will grow to be nearly identical to the parent plant. A few however, will be slightly different. Some variations are undesirable: smaller size, bitter taste, vulnerability to disease and so on. Other variations are highly valued! Thicker, sweeter leaves for example. If a farmer only allows the best plants to reproduce and give seeds, small positive changes will add up over multiple generations, eventually producing a dramatically superior vegetable.

 You might be surprised to hear that broccoli, cauliflower, kale, Brussel sprouts, and cabbages, are all just different breeds of a single type of weed! The evolution of this original plant into all the different kinds we see today was carefully guided by different farmers around the world, who simply selected different traits to evolve. It's important to say that the farmer himself doesn't actually create anything. The farmer simply chooses which of those new creations are allowed to reproduce, and which are not. 

Darwin proposed that nature itself is also capable of selection.

It may not have an intelligent brain like a farmer, but it is an extremely dangerous environment to live in. There are many ways you could die. You could get infected, you could get eaten, you could freeze to death, burn in the heat, drown, die of exhaustion and so on.

When parents produce a variety of offspring, nature, 

simply by being so dangerous and difficult to survive in, decides which of those variations get to live and reproduce, and which do not, like a farmer would. Over multiple generations, creatures became more and more fit for survival and reproduction within their specific habitats.

I called this process Natural Selection. Since I first put forth this idea in the mid 1800s, Natural Selection has been studied and witnessed numerous times in nature and in labs across the globe. 

What started out as a mere idea is now officially an observable fact! My discovery has greatly expanded the understanding of the natural world, finally allowing scientists to seriously consider the idea of Common Descent.

Through this simple ongoing process, nature,  even though it may not have a thinking mind,  is capable of producing incredibly complex  and beautiful creations.