Okay, here's layman's terms for you: imagine a factory that has an unlimited supply of fresh workers. Now, this factory is not at all selective in hiring, not one bit. They have a more straightforward method of quality control. If a worker isn't putting out, they just put a bullet into his brain and replace him with a new worker. That's not all, though because, you see, there's only so much work that the factory needs to have done. Therefore, if one worker is doing the work of two other workers, the other two workers are also shot dead, even if they were doing their best to be productive. Sometimes, workers in this factory get in a team together, and some of THESE workers won't directly do the work. Instead, they will do things to keep up the team's morale, negotiate with the bosses to get more of the work entrusted to them, manage the team's image, dedicate themselves to building tools that improve overall performance manifold, and help to root out lazy or dishonest workers elsewhere in exchange for earning forgiveness from the factory during hard times. The factory, then, doesn't really have to do anything at all other than continue nixing workers who are found to be useless, and it's left up to the workers to come up with innovative ways of getting things done. This is somewhat equivalent to natural selection.
This really doesn't come into play until you already have the very first self-replicating organisms, though. After you've got your first few replicators, natural selection works fine, but actually GETTING them isn't so easy. However, there are numerous conditions in nature that are actually conducive to the organization of matter. Though complex molecules are naturally degenerative, a high input of energy forces levels of ionization that are promotive of reorganization. As long as an environment has a nearly constant energy input, the breaking down of molecules would just result in yet more potentiality for reorganization. The advent of DNA may have been a result of a deterioration of a form of "sexual" reproduction between RNA-based organisms that had lost their ability to replicate on their own. As these sexually reproducing RNA organisms further deteriorated in their ability to even survive on their own, they would eventually be locked to each other permanently as one molecule. Though the RNA strands in and of themselves had lost much of their stand-alone sophistication, a greater level of sophistication and stability was gained as a result. Now consider this: for millions of years, these DNA-based organisms managed to survive just fine through rapid "asexual" reproduction, this constant energy input constantly forcing levels of ionization that do not allow for a net trend of deterioration. However, these DNA-based organisms could only survive by spamming their environment with enough rough copies of themselves to compensate for the trend toward deterioration. Now, we're still going on the assumption that stand-alone complexity will always trend toward breaking down on an individual basis. Natural selection is not nice to individuals. Eventually, the only way for some of these organisms to even preserve their identity would be for many of them to expend all of their energy and resources for the sake of making sure that their heritage could survive. This, of course, is what we call the multi-cellular organism. The multi-cellular organism is really nothing but a bunch of cripples banding together to save themselves from extinction. On an individual basis, these pathetic things can't even survive for long. Eventually, they end up breaking down into the genetically assigned roles within the context of a multi-cellular organism, doomed for their own information to be lost from the very beginning of their lives. Even the multi-cellular organism, however, is fated to rely upon other organisms for the survival of its identity, in the form of sexual reproduction as we know it. You see, eventually there comes a point that this whole, complicated organism, over the course of its entire lifetime, can only reproduce HALF of a cell that can truly carry the information needed for the continuation of this organism's level of organization. This pathetic thing can't even make a full copy of itself. Isn't it pitiful? Such a failure in stand-alone reproductive potential is just shameful. We should be embarrassed to call ourselves sexually reproducing, multi-cellular organisms. The only thing that helps us to save face is that, elsewhere in nature, the breakdown has continued in the form of organisms that can only survive by banding together in hives and colonies, such as ants and bees. We should feel sorry for these poor things, for they have lost more of their independence than we have ever imagined. Looking at it another way, however, they are the next logical evolutionary step. Look at how sophisticated an ant colony really is. Ants are arguably one of the most sophisticated organisms in the universe, but they're also arguably the most pathetic sellouts in nature. Eventually, we may even see these losers having to send their genes out to other colonies just to maintain their genetic integrity. When that happens, watch out because, when that occassion comes, it'll only be a matter of time before this new species of ant begins organizing on a greater level still. We'll see ant colonies banding together almost like one organism, doing things with each other's help that humans can only imagine in their wildest dreams.
Evolution is a process of creative destruction and novel incapacitation. We are death machines, programmed from the very beginning of our existence to rot and to die. For us not to die would be a defiance of nature. It would be to spit in the face of creation. However, think of it this way: if humans manage to gain the ability to live all but forever through the exploitation of technology, we will have only continued the creative process, for we will have lost our ability to exist without our inventions. Like those who came before us, we will become a race of dependents, crippled from the very beginning of our lives. That, my friend, is evolution.
