Evolution is highly debated and is increasingly being called into question for a variety of reasons.
First of all, *evolution* is not in question. We know that evolution exists because living things are evolving
right now, in our lifetimes. Why do you think viruses mutate? Anyways, you probably already realize that the debate focuses on the *historical* evidence, rather than the realities of evolution.
An evolutionary argument for humans can be "called into question," for only 2 reasons:
1.) You believe that the skeletons we have excavated of pre-modern man are either fake or planted by God.
2.) You cling to the argument of 'irreducible complexity' (which ebola! stated).
Speaking from an empiricist's standpoint, I think the whole Irreducible complexity argument is striking. Nothing assembles itself right? Basically, irreducible complexity is just a re-hash of Paley's watchmaker argument. The chance that something with as few as 3 or 4 necessary parts could assemble itself in one "dice roll," is of course going to be rare. And the people espousing this viewpoing love to spout off incredibly low, and long numbers....and then make colorful analogies to further illustrate just how low the probablity is. This is all a smoke-screen. Think about the human eye (or any rod+cone and concave eye). It is so complex.......and irreducibly so, right? WRONG. Think of the first life-form ever to, by chance, be born with a photo-sensitive cell. It isn't just an abnormality. It actually functions and helps the lifeform find food sources. Maybe it allowed certain life-forms that didn't have good spatial ability (don't know what direction is up/down, can't feel gravitational cycles accurately), to finally be able to track the cycle of night and day, therefore allowing it to find food in a new place, or whatever. That is a dubious example, but the point is....If the genetic mutation which leads to an irreducibly complex system actually has functionality before it is complete, then irreducibly complex systems aren't so much of a problem for evolution. Obviously there are real-world examples where this is the case, and of course there are "true" irreducibly complex systems for which I have no answer. That is why I still find the argument interesting, because there are systems where I can't really see how they could work without every single part. Take for example, an immune system (or any irreducibly complex system which is composed mostly of cascading chemical reactions). Thousands of proteins, catalysts, enzymes, proteases, RNA, genes, many of which when fighting a disease require signals before they act, signals which are dependant upon still other chemicals acting first, and so on. Remove one enzyme and the whole thing ceases to function.
But just because something is unlikely in *one* way (irreducible complexity), doesn't mean it is JUST AS unlikely in all other ways. For example, imagine an evolving mouse-trap where on each dice-roll, it tries to assemble itself. It must have a base, a spring, a spring release, a bar, etc. Irreducible complexity arguments typically assume an "all-or-nothing" scenario. If the mouse-trap isn't completely put together, throw out that chance completely. But we know that individual types of proteins can mutate over time. What if the mouse-trap by chance assembled itself perfectly but with one error: the spring isn't strong enough to immobilize a mouse. Imagine that this is because some important protein in the spring has a 2 or 3 codon amino acid flaw resulting in a bad protein (there are human disease like this). Then imagine that in the
very next dice roll, the amino acid gets translated correctly, resulting in the stronger protein and the tighter spring. Of course this is an outlandish example, but it shows one aspect that the irreducible complexity argument may not address. The *system* may be highly complex, but errors in the system are very simple.
Now moving on to the other reason that people call evolution "into question." It is so ridiculous that I don't think it's worth writing much on. It's an egotistical conspiracy theory:
"The skeletons were planted, I know it. The paleontologists, in concert with the CIA, Satan, and the atheists, planted the fossils which give evidence of evolution....just so they could destroy the institution of God."
So to conclude, evolution isn't being called into question for a "variety" of reasons, only two. Of those, one is compelling but nowhere near enough to actually deny evolution (even it's proponents admit this). The other reason is just plain stupid.
And I suppose there is a 3rd reason, but it's also stupid. Some people say, "I'll admit there is a human fossil-record. But there are gaps in that record, so I won't believe it until all the gaps are filled."
So then if we dig into the ground and as we dig deeper find 21, 18, 15, 14, 13, 9, 8, 5, 3, 1, then the person refuses to believe they are related to each other until we find 20, 19, 17, 16, 12, 11, 10, 7, 6, 4, and 2.