Most scientists think evolution is the most powerful theory in biology. I would agree entirely. Scientists have used the understanding they have gained from the theory of evolution to create new medicines and develop new strains of crops among many other things. Together these two broad advances have made our lives immeasurably better.
However, as an explanation for diversification and speciation it has some serious problems. Now, I don't mean to say that evolution has not occurred. That would be another discussion. What I mean is that evolution as a wholly natural and unguided process accounting for the tremendous diversity of life on earth is highly improbable. Let's take a look.
Fundamental to all living things is DNA. DNA is the most complex and organized thing we know of in the universe. Your DNA and mine instructs our cells to grow into the highly specialized organs that make up our bodies. It tells my eyes to be blue and yours to be brown. It determines whether I will lose my hair as I get older or just turn gray.
The information stored in every single human cells' DNA is estimated to be about 1.5 gigabytes. That doesn't sound like much today. (There is a bit of debate about that. Some describe that 1.5 GB as a "zipped file" in which a great deal more information is stored than 1.5 GB.) The computer I am writing on would store that easily. But compared to something I can visualize, 1 GB in printed books could fill a pickup truck. How many bytes for?.
A bacterium, which is somewhat similar to the presumed first living thing, has about 0.1 % of a human's DNA. Genomes of Bacteria. Put in terms I can understand, that would be one book compared to 1000. Now, the problem comes when I try to understand how the information in the bacterium could increase to the information in the human cell.
Roughly, this is how evolution is supposed to work. Mutations provide new information. That is a random process. Natural selection eliminates information that doesn't work, leaving information that in some way benefits the organism. (I know this is extremely simplified.)
So I start with a book full of information. Four billion years later I have a truck load. Let's see how that might work.
Pick any book on your shelf. Start with an encyclopedia, if you like. Find the last word in the book and add one random letter. Add another and another until you have, maybe, a dozen random letters following the last word in the book. Now, cross out all the letters that don't add up to a new word.
I'll do that with a book titled To Change the World (seems appropriate for our purpose). The last word is better. I'll add a dozen random letters: ejoyclthmapl. If I now cross out the letters that don't make sense, I am left with joy and map. I should note that I've been unusually lucky. Having two words in the first twelve random letters is a far larger percentage than anyone would expect in the process of mutation and natural selection. The fact is, only a very small percentage of mutations provide useful additional information. But even so, do the two words look to you as though they could become the first two words in another page of the book (or any book)? I doubt it.
However, if a purely mindless evolution is to create 1000 books from 1 book, that is what must have happened thousands and thousands and thousands of times over. Does anyone believe that could happen? I doubt it.
So since evolutionary scientists tell us that it did happen, I have to ask how? How could the extraordinarily improbable (on the order of being statistically impossible) have happened?
The only way that I can imagine that happening is if there were an author. If there were an author, the impossible becomes perfectly possible, even expected.
My conclusion is that if mutation and natural selection is the process by which the human genome came to be, an extraordinarily intelligent author had to have directed the process. My evolutionist friends will, of course, ask me how that presumed author might have done this, and I have no answer to that. But I don't need to be able to answer the question how. (Actually, evolutionists cannot answer that how question either.) I only have to know that there is no other logical answer than an author ordered it. I am happy to call that author God.