In my previous post, I discussed the proper way to apply the Second Law of Thermodynamics to a simple process: the freezing of water in a bucket. Now I want to apply the Second Law of Thermodynamics to the process of evolution. This is a difficult thing to do, because currently, there is no accepted mechanism for the process of evolution. Evolution might occur according to the Neo-Darwinian Synthesis; it might occur via punctuated equilibrium; it might occur according to the evo-devo view; it might occur as a result of facilitated variation; it might occur by some as yet undiscovered mechanism; or it might occur as a result of a combination of all or some of these mechanisms.
Even though there is no agreed-upon mechanism for evolution, some general statements can be made about the supposed process, and that should be enough to allow us to roughly apply the Second Law of Thermodynamics to it. In general, evolution says that organisms increase in complexity over time. A single-celled organism, for example, eventually developed the ability (through some as yet unknown process) to cooperate with other cells, which eventually led to a multicelled organism. Clearly, a multicelled organism is more complex than a single-celled organism, so via that unknown process, “simpler” single-celled organisms gave rise to “more complex” multicelled organisms. These multicelled organisms began to develop (once again, through some as yet unknown process) more “advanced” features, so that eventually a large diversity of life formed.
The longer evolution had to work through its unknown process, the more complex living creatures became. Thus, while it took some time for the evolutionary process to create relatively “simple” multicelled creatures, it took more time for evolution to produce complex invertebrates, and it took more time for evolution to produce vertebrates. The more “advanced” the vertebrate, the longer it took for evolution to produce it.
So, despite the fact that evolutionists cannot produce a mechanism for how all this supposedly happened, we can at least say evolution requires that over time, living organisms became more and more complex. While there is not a direct connection between biological complexity and entropy, it is generally thought that increasing complex genomes result in decreased entropy (see figs. 3 and 4 in that article). Assuming this is correct, then, evolution requires that the entropy of evolving creatures decreases over time.
Like the freezing of water discussed in my previous post, this seems at first glance to violate the Second Law of Thermodynamics. As a result, it has caused a lot of well-meaning creationists to say that the Second Law forbids evolution. However, just as is the case with the freezing of water, that’s simply not true. As the freezing of water illustrates, a system can, indeed, decrease in entropy, as long as there is a corresponding increase in the entropy of the surroundings that at least offsets the decrease in entropy of the system.
So in the end, we see that the Second Law of Thermodynamics does not forbid evolution. However, it does impose a constraint. If there ever comes a time at which a detailed mechanism for evolution is seriously proposed, that mechanism must include a process by which the loss of entropy in an evolving genome is offset by a gain in entropy for the surroundings. Of course, the hypothesis of evolution is far from the point at which a serious mechanism can be proposed. However, if that ever happens, the thermodynamics must be considered.
Now remember, the whole reason I started this two-part post was because of an article cited by Dr. Hunter in one of his blog posts. As I noted before, this article comes to the correct conclusion (evolution is not inconsistent with the Second Law), but for the wrong reasons. It essentially says that the sun’s heating of the earth (and the earth’s subsequent loss of energy) increases the entropy of the earth significantly more than the process of evolution decreases the entropy of the earth, and therefore evolution can occur.
Can you see the problem with this argument? It assumes that the only issue is the overall entropy budget of the universe. As long as the universe’s entropy continues to increase, the fact that some portion of the universe decreases in entropy is not important. That might sound like what I have been saying all along, but it isn’t. As I stressed in the previous post, if the entropy of a system decreases, the surroundings must experience a corresponding increase in entropy. The paper in question ignores the fact that the increase in entropy of the surroundings must correspond to the decrease in entropy of the system.
In the paper, the author argues that one process (the heating of the earth by the sun and the earth’s subsequent loss of energy) allows a completely unrelated process (biological evolution) to occur, because the first process increases the entropy of the universe more than the second process decreases the entropy of the universe. However, this is nonsensical. The process that offsets any entropy loss must correspond to the process that caused the entropy loss in the first place.
Think about it this way. If the total entropy budget of the universe was the only issue, I would be able to freeze water at 1 degree C by starting a fire somewhere far away from the bucket. After all, the fire will increase the entropy of the universe a lot more than the freezing water will decrease the entropy of the universe. Thus, the total entropy of the universe will still increase, as long as a fire is started. Despite this fact, starting a fire somewhere else will not freeze water at 1 degree Celsius, because every process that occurs must obey the Second Law. The reason water freezes at 0 Celsius is that the process of water freezing at that temperature causes both an entropy loss and an offsetting entropy gain for the universe. As a result, there is no entropy change to the universe during that specific process.
So in the end, the fact that the sun is heating up the earth and causing all sorts of entropy increases has no bearing on whether or not the process of evolution can occur under the guidelines of the Second Law. Each step in the hypothetical process of evolution must be consistent with the Second Law, regardless of what the sun is doing to the earth. While it is certainly possible to construct a scenario by which this happens, the paper linked above does no such thing.
It is unfortunate that in their rush to “defend” the cherished dogma of evolution, the American Journal of Physics ended up promoting a terrible misconception about the Second Law of Thermodynamics.