Evolution and intelligent design are controversial, complicated topics. I am not a creationist, but I am sympathetic to some of the criticisms leveled at evolution (some from intelligent design theorists, some from within the field itself). Research on the origin of life, in particular, has some difficult conceptual issues to face. Here is one that I find interesting:
First, I want you to look at the computer that you are using right now to view this page. Whether it is a laptop or a desktop computer, you are looking at something rather special. Here's what I mean: your computer is made of ordinary elements. Silicon, aluminum, iron, carbon, etc. The elements in your computer are not any different from elements you could find anywhere else. But, in this case, they are allowing you to connect to a world-wide network of information and view things like this webpage. Why? Nothing in the elements themselves dictate this sort of function. One could have all the appropriate elements and compounds together, but there would be no tendency for a computer to emerge. This means that these elements, along with the physical and chemical laws that govern their behavior, allow a computer to be built out of them. However, the raw materials themselves along with the natural laws that govern them are not capable of creating a computer. We can therefore say that computers are contingent; that is, the existence of computers cannot be explained by any known scientific laws, and nothing in the universe requires that they exist. Contrast this to, say, the gravitational attraction between the Earth and the Sun. In our universe, the laws (of gravity, in this case) demand a force of attraction (in Newtonian terms) of a certain magnitude between these two masses. They have no choice in the matter. A computer, on the other hand, is entirely contingent. Your computer's elements have been organized in a complicated, specific arrangement that results in the functional computer you have in front of you, but nothing in the physics or chemistry of those elements led to this specific arrangement.
OK, so what does this have to do with the origin of life? It turns out that biological life, as we know it, is contingent. DNA, for example, contains the genetic information that you or I or any living thing are built according to. DNA can be said to contain the blueprints of an organism. It consists of long strands of what are called nucleotides, major parts of which are made of nucleobases such as adenine (A), cytosine (C), guanine (G), and thymine (T). The arrangement of these nucleobases is largely responsible for the information contained in the strands of DNA. For a simple analogy, think of the words in an encyclopedia, or in this post. The arrangement of the letters (of the English alphabet, in this case) determines the information contained in a written entry. Different arrangement, different meaning. Different arrangements of the four "letters" of the genetic language (A, C, G, T) are responsible for all of the different organisms we see on earth. Now, this is not merely an analogy; DNA is not like a language, it is a language. Contemporary biologists have come to realize that when they speak of genes, they are speaking of information, not something physical. Here's where it gets interesting: information transcends physics and chemistry.
I don't mean this in some mystical, metaphysical way. Think about it. When you write a journal entry in your notebook, you are using ink and paper to represent information. But the ink and paper itself cannot be responsible for the information content, nor can the ink and paper itself said to be the information. Rather, the ink and paper happen to be the physical medium for embodying that information. The information itself transcends the physical and chemical. At first the information was in your mind, then on your paper, and then could be typed into a computer document, then transferred onto a thumb drive, etc.
In each case the information was being physically stored in a medium, but it is clear that the physical media are not themselves responsible for the creation of the information. In fact, the physical medium must be neutral, or flexible, in order for it to usefully store information. Consider your ink and paper again. If whenever you wrote the letter "t", the physical properties of the ink and paper forced the next bit of ink to form the letter "s", then you would have a very difficult time writing anything meaningful. The physical and chemical properties would determine the content of the paper, and your journal entries would be limited to repetitive strings of letters. Physical and chemical laws are good at repetition (a rock will always fall the same way, bits of lava will crystallize again and again in the same pattern), but cannot explain the origin of complex, specific information.
Let's get back to biology: our DNA strands, with the arrangement of our bases (letters) A,C,G, and T, cannot be explained by any physical or chemical laws. Like the ink and paper, the physical laws of the DNA strand itself allow a near infinite variety of arrangements of DNA letters. How then, can the materialist explain the origin of genetic information? If one is a materialist (i.e. one who holds that the physical, or nature, is all that exists), one is stuck trying to explain the origin of genetic information in terms of the known physical and chemical laws of the genetic molecules themselves. This is very literally like trying to explain this essay by appealing to the physics and chemistry of the molecules in the computer screen, or like trying to explain a newspaper's information content in terms of the physical and chemical properties of the ink and paper. As we have seen, the physical medium itself must remain neutral on the arrangement of letters or else the medium is useless for information storage. A neutral physical medium cannot explain why we see one particular arrangement and not another.
[In case the reader is wondering, chance cannot explain the first bit of genetic information; the probabilities of accidents resulting in even the "simplest" self-replicating cell are incredibly low (a single cell in your body contains vastly more information than Encyclopedia Britannica). Origin of life researchers do not consider chance to be a viable explanation, but are investigating scenarios where unique chemical conditions can hopefully explain the emergence of the first self-replicating machine.]
I am not trying to suggest that materialists are stupid; I am merely drawing attention to an important conceptual problem. If you are familiar at all with origin of life research then you know that scientists have investigated a huge range of possible scenarios leading to the origin of the first cell with some genetic information. While this research is extensive and informative, it is also above all strongly inconclusive. See Shapiro's Origins for a devastating critique, or Schopf's Life's Origin for an optimistic but honest assessment of the research. I am not calling for origin of life researchers to quit and say "God did it." I am, however, suggesting that researchers should pay careful attention to criticisms like those discussed above. It is possible that new laws will be discovered that can shed light on this problem. Only time will tell if the origin of life will eventually be explicable in physical and chemical terms. I will enjoy following along to find out.