Second Law Silliness

Been working on the evolutionary biology track in my forthcoming philosophy of science textbook, Methods and Models, and in fairly quick order came across two instances of the argument against evolution based on entropy. It's probably worth making clear why this argument fails in a way that folks can quickly debunk it.

The argument is this: Evolution's central claim is that species adapt to environmental factors. The evolutionary description of the origin of life, therefore, takes us from species of simple one-celled organisms to more and more complex, better adapted species. Advocates of evolution hold that this process occurs in accord with the laws of nature, but the second law of thermodynamics holds that at all times disorder increases. But evolution, to the contrary, holds that over time biological order increases. Therefore, evolution violates the second law of thermodynamics and therefore cannot occur given our best understanding of the laws of nature.

First, the second law of thermodynamics holds that in a closed system, entropy tends to increase. What does this mean? Entropy is a measure of the number of possible states a system may be in. Suppose you had two wooden eggs in an egg carton and you put one in the hole on the bottom right and one in the hole on the top left. You know where those eggs are. Now you shake the carton and with each shake each egg can move one hole in any direction, but you don't know which direction. With one shake, they could still be in their original holes or each could be in one of the three surrounding holes. With two shakes, the number of holes they could be in is larger. That's an increase in entropy. Now, there's always the chance on a given shake that the eggs will be back in their original holes and the order will be restored, so entropy can spontaneously decrease, but in general it tends to increase.

We can always restore order by opening the carton and replacing the eggs where they go. That takes energy, but energy can always be used to decrease entropy. That's what happens when we clean our desks or run an air conditioner.

That is why the first clause is there in the second law -- "in a closed system." What that means is a system in which no additional energy is added because in an open system, the energy could be used to decrease entropy and increase order. So the second law only holds in systems in which no additional energy is added.

Life exists on a planet we call "The Earth" and the earth is not a closed system, there is energy added to it by a large, hot, yellow ball in the sky which goes by the technical name "The Sun." The sun brings energy to the earth and this energy is fixed by plants by photosynthesis. The plants are then eaten which brings energy to the animals that eat them and the animals that eat these animals then acquire some of that energy for themselves. Hence, energy is always being added into the system which then is used to decrease entropy in the organisms which participate in ecosystems exhibiting pressures that result in natural and sexual selection and thereby we get evolution in perfect harmony with the second law of thermodynamics.

But what if we don't look at the earth which is not a closed system, but the solar system as a whole? Since the sun is a part of the system, it is closed and since the earth is a part of it, doesn't the second law hold that there should be no life in the solar system writ large and therefore on the earth which is a part of it? No. Energy transfers within subsystems will cause there to be pockets of higher and lower entropies within the system while the overall entropy of the whole still tends to increase.

So, appeals to the second law of thermodynamics is in no way worrisome to the possibility of species adapting to changing environments by random genetic mutation and natural selection.