Much of the evolutionary theory is based on natural selection.
How does this process really work? This article will help clarify exactly what is wrong and what is right about this popular foundational theory.
To begin with, we need to understand what natural selection IS and what it ISN'T. Natural selection only works if there is more than one kind of creature in existence. This may seem like an overly simplified statement, but it actually strikes at the heart of a huge misconception on the part of many. 
Natural selection is an eliminator. In other words, if there are two variations of a creature, the theory goes that natural selection chooses the fittest—or best—and allows the unfittest—or weakest—to become extinct.
This goes against the evolutionary concept of more and more varied species evolving through natural selection, as natural selection creates less and less varied species. Without a pre-existing variation of species, evolution by natural selection would be impossible. Natural selection cannot explain the abundance of species we currently see on our planet if all these species stemmed from a single ancestor.
The variation that Darwin observed in the finches and other organisms on his voyage with the Beagle led to the concept of evolution by natural selection. This is significant because of the mindset during Darwin's time.
At that time, the Christian European concept of Creation was that God had created immutable, unchangeable species. It was believed that each species was created individually by God exactly as it appears today, and could not change or develop variation. The way species were, and still are, classified uses this concept to a large extent.
Before we can even consider natural selection
as an evolutionary force, we need to make several assumptions.
We must assume that millions of chance mutations took place in cells and genes making an organism from which to choose. We must also assume that the genes for the varying cells in our bodies will need to have come about by chance.
By chance, these cells must have developed genes that permit the cells to communicate or work together, or else the organism will not even work. By chance, genes that switch the cell's functions on or off also need appear. All these chance mutations need to occur before an organism can be "selected" by natural selection, because otherwise, there is no organism to choose from. But, a choice requires at least two options. So, all those chance mutations need to occur a second time to create a second organism from which to then choose from.
Is it logical to assume all these chance mutations took place without checking to see if they are even probable?
And how can a process (natural selection) that eliminates species actually make more and more? It is NOT possible. All this requires a large amount of faith in the god of "chance," and in an occurrence whose improbability is enormous. Read more in Natural Selection as a Creative Force