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itself. Things being the way they are out there (or way down in there), these copies are not perfect. In the same way, you can tell the difference between an original document and a copy of the document made with a copy machine, it’s very difficult in nature to make a perfect copy. Those small changes in DNA that occur during an organism’s developmental stage result in the organism being just slightly different from its parents or parent organism. They introduce variation within a population. These changes can help an organism live and eventually reproduce, hinder the organism’s reproduction, or produce no noticeable difference. You can see why people might think these changes result from conscious or willful acts, but they don’t.
    The changes that help an organism reproduce stay with the organism’s offspring; beneficial changes get passed on in the DNA. When the offspring, in turn, reproduce, they have that beneficial characteristic, and that helps them produce offspring themselves later on. The changes that hinder an organism keep some fraction of that organism’s population from reproducing. So hindering changes don’t get passed on; they disappear from future versions of that organism’s DNA. The changes that don’t make any difference—don’t make any difference. They get passed on as well.
    In general, when energy becomes available to an organism, that energy helps an organism survive and reproduce. Incoming energy (from food or sunlight) can drive and create a beneficial change, which can lead to increased complexity in the offspring of those living things. Once Charles Darwin saw this connection, he realized what a powerful idea it is.
    You can contrast the system in nature with a system in a human-built organization like a corporation. Hardly anything happens to benefit an organization unless someone somewhere makes a choice. Very few changes happen organically, that is, from the organization being affected automatically. Someone has to step in and hire or fire, invest or divest, buy or sell, or else nothing happens. Certainly nothing happens automatically to make a system more complex in a good way. You might say that human organizations depend on an intelligent designer.
    As a corporation grows, different divisions add systems, paperwork, forms to fill out, hoops to jump through, and so on, to help their division get things done. At some point a manager might come in and analyze that the organization is top-heavy, too many middle managers managing too few people below them. He or she might determine that there is too much paperwork, too much redundant storage of transactions or records, and so on. Then that manager starts cutting pieces off or trying to streamline things.
    It doesn’t work that way in evolution. If you have a system that holds an organism back and keeps it from reproducing with success, that organism will not pass its genes to the next generation. Nobody has to decide anything. Although a change in a gene usually happens at random, the next generation of that gene is subject to forces that are anything but random. You’ve got the right combination of genes or you don’t. You’re still in the game, or you’re not. We call it selection pressure; it determines which genes get through.
    Many creationists and science deniers, especially in the United States, cite randomness as part of the process of evolution and go on to insist that since evolution is random it cannot explain the rich complexity of life. This is essentially another form of the thermodynamics argument I talked about in the previous chapter. Creationists often use the example of a hypothetical tornado swirling its way through a hypothetical junkyard whose contents include all the pieces to build one of my beloved old 747s. (This is sometimes called the junkyard tornado argument.) What are the chances, they ask, that you’d end up with a perfectly assembled, operable