The 12 days of evolution. #8: Evolution and thermodynamics

December 28, 2015 • 11:00 am

Here’s the Eighth Day of Creation, or rather, the eighth episode in the PBS/It’s Okay to be Smart series on “The Twelve Days of Evolution.” In effect, the episodes each aim to debunk one creationist misconception (or lie). In this case it’s the old claim that evolution violates the Second Law of Thermodynamics. Let’s review that law, as limned by Wikipedia:

The second law of thermodynamics states that in every real process the sum of the entropies of all participating bodies is increased. In the idealized limiting case of a reversible process, this sum remains unchanged. The increase in entropy accounts for the irreversibility of natural processes, and the asymmetry between future and past.

This supposedly makes evolution impossible, as evolution is the production of order from disorder: a reduction in the entropy of life, and an increase in order, if you begin the process molecules floating in water. The solution, as the video shows (and all of us know) is that the reduced entropy produced by evolution is paid for by a greater increase in entropy in the cosmos as a whole. That’s because the Earth is not a closed system, and Sun’s increasing entropy is necessary to fuel Earth’s evolution 93 million miles away. Here’s the short video:

My sole beef with this episode is that I think the cookie example, in which baked cookies are supposed to be analogs of the products of evolution, is weak. In fact, I’d need a physicist to convince me that the transformation of cookie dough to edible cookies requires a loss of entropy, even though I understand that the stove’s heat is an increase in entropy. So it goes; perhaps readers can clarify.

34 thoughts on “The 12 days of evolution. #8: Evolution and thermodynamics

  1. A major problem is that the video equals entropy increase with disorder increase. That is happening in most systems, but very constrained ones like cell compartments may instead experience an order increase. If you discuss universal laws you better get them right!

    Also I would have liked to see more weight put into how reproduction and development are major entropy producers, and evolution imperceptible on top of that.

    Re baking cookies, as long as the process is irreversible there is an entropy flow to the universe. You push some endothermic reactions over the energy hill, and some – but not all – would be spontaneous (entropy producing).

    A spontaneous reaction can be entropy decreasing in the system, as long as the system and its surroundings (universe) sees an entropy increase.

    1. Oh, references. I guess I recommend Wikipedia on the thermodynamics of chemical reaction, though I admit a course in biochemistry is helpful.

      Re how increase in entropy # (always) increase in disorder, I have linked the research so many times here so a search would suffice.

    2. ERRATA: As eric reminded me by his comments below, I confused exergonic and spontaneous processes. I made a mess, which sometimes happens in baking.

      I guess I need to revisit that biochemistry course…

  2. Cooking an egg is a simpler example. Initially the proteins in the egg are free to diffuse about (initial entropy) and then the heat denatures the proteins (more entropy than folded proteins) and then the proteins react with each other forming a network of interconnected proteins (less entropy than free, folded proteins).

    This ignores all the non-protein parts of the egg but I think captures the basic argument.

    1. Yep. Another (also from biochem) would be an examination of what happens to sugars. They tend to start out simple… small freely-flowing molecules of glucose / sucrose, etc. After making (at least baked) cookies, you will have many of them forming larger, fixed complexes of sugars & carbohydrates. If you end up burning the cookies, you’d go sliding off the entropy scale again, to simple stuff (burned carbon… liberated gases), but at some point there is a sweet spot where chemical complexity increased. (even though, as is the case here, that molecular movement decreases).

  3. Unbaking cookies would be a violation of the Second Law. The example is correct, though unreasonably un-heuristic and too subtle.

  4. I’m not so sure the cookie example is good either, but if someone told me it was a good example and asked me to give my best explanation as to why, here’s what I’d probably say:

    Supporting fact 1: spontaneous isolated processes always increase entropy.

    Supporting fact 2: entropy-decreasing reactions must be endothermic or non-spontaneous. Another way to put this is “endothermic, spontaneous, or increasing entropy – you can only pick two.”

    Supporting fact 3: in general, entropy also increases as you go from solid to liquid to gas. That’s not an ironclad rule, but a general rule of thumb.

    Argument: since the reaction “dough to baked cookie” appears to be a non-spontaneous, endothermic reaction that takes a semi-liquid and turns it into a solid, it’s a decrease in entropy.

  5. An example that may be easier to understand and apply is a refrigerator.

    You can cool the air and the food inside the refrigerator, but doing so require an input of energy (electrical power) and the ability to release enough heat into the surrounding room (usually via metal spines on the back of the refrigerator) to pay the Entropy Toll.

    1. I think they were trying to show a change in state of some object as a local decrease in entropy. A refrigerator isn’t as good as a cookie in terms of that analogy.

      Frankly life is the best ‘analogy’ for life. Everyone understands that if you stop eating and pooping, you stop period. A constant flow of energy through our systems is required for those systems to build and maintain complex structures, and most people understand this, albeit they do so in layperson’s terms not in technical terms.

    1. I may as well quote my beef with Carroll’s article, which is roughly the same, when we look at statistics we need the “usually” flag. Hence it is also true that increase in entropy means increase in disorder, but only “usually”:

      “But crowded tightly, the particles began forming crystal structures like atoms do — even though they couldn’t make bonds. These ordered crystals had to be the high-entropy arrangements, too.

      Glotzer explains that this isn’t really disorder creating order — entropy needs its image updated. Instead, she describes it as a measure of possibilities. … In this case, ordered arrangements produce the most possibilities, the most options. It’s counterintuitive, to be sure,” Glotzer said.” [ ]

  6. I am not sure, but perhaps the baked cookie has experienced an increase in the # of hydrogen bonds between long polymers, converting the squishy cookie dough –> firm, baked cookies. This would require an addition of heat to the system to get the molecules over the activation energy needed to form hydrogen bonds.

  7. Sean Carroll’s blog post titled “Evollution and the Second Law” is worth reading in its entirety…but I quoted the parts that I found especially interesting below.
    “… Consider the entire biomass of the Earth – all of the molecules that are found in living organisms of any type…if it were in thermal equilibrium…plugging in the numbers…we find that its maximum entropy is 10^44…

    …So the largest conceivable change in entropy that would be required to take a completely disordered collection of molecules the size of our biomass and turn them into absolutely any configuration at all – including the actual ecosystem we currently have – is 10^44. If the evolution of life is consistent with the Second Law, it must be the case that the Earth has generated more entropy over the course of life’s evolution by converting high-energy photons into low-energy ones than it has decreased entropy by creating life. The number 10^44 is certainly an overly generous estimate – we don’t have to generate nearly that much entropy, but if we can generate that much, the Second Law is in good shape.

    How long does it take to generate that much entropy by converting useful solar energy into useless radiated heat? The answer…is: about one year. Every year, if we were really efficient, we could take an undifferentiated mass as large as the entire biosphere and arrange it in a configuration with as small an entropy as we can imagine. In reality, life has evolved over billions of years, and the total entropy of the “Sun + Earth (including life) + escaping radiation” system has increased by quite a bit. So the Second Law is perfectly consistent with life as we know it…”

  8. Here is a really good reference about the second law of thermodynamics:

    and I love this quote:

    “Entropy change doesn’t measure “disorder”! (What are the dimensions of “disorder”? Malarkeys per minute or some such nonsense? The scientific dimensions of entropy change are joules/Kelvin.)”

  9. A better definition is that entropy is a measure of the number of microstates (actually the logarithm thereof) consistent with a given macrostate. The number of microstates consistent with the cookies macrostate is fewer than the number of microstates consistent with the same mass as a lump of cookie dough.

    So the cookies have lower entropy. Of course, the entropy of the cookie monster increases when he gobbles them–nyum, nyum, nyum.

  10. Saturday Morning Breakfast Cereal cartoon had a nice rebuttal to creationists and their misunderstanding about thermodynamics:

  11. Thinking of entropy in terms of order/disorder as a heuristic has displaced the old thermo-dynamics view which I think is more intuitive. Consider a gas engine. Total energy input goes to work i.e. particles pushing the piston in a useful way and heat i.e. particles going every which way not doing what is intended. The heat corresponds to the increase in disorder i.e. increased entropy. The same equation is applicable to chemical reaction, signal/noise ratio, order/disorder etc. The same model is useful in different ways we try to describe reality. Another simple way to think of entropy is that available energy is unavoidably partitioned into less concentrated states (more things, more disorder) from a given state and to reverse that direction there must be an energy source. This heuristic is of course simplified but can be mad rigorous.

  12. Putting aside cookie dough and eggs for a moment and going back to the matter at hand, which is the Earth, I’m not sure we need to say more than that The 2nd law of Thermodynamics applies to CLOSED SYSTEMS. Finished.

    As mentioned in the post, the Earth is NOT a closed system, receiving ALOT of external energy from the sun.

    Not sure why this would be hard to understand (and not saying this in any condescending way).

    Carl Kruse

    1. The process on Earth that generates the most entropy is simply the absorption of sunlight and its reemission as lower temperature radiation. Any decrease in entropy in living matter is utterly negligible in comparison.

      BTW, the entropy of the Sun is decreasing with time. I’m not sure if any creationists have claimed this means the sun cannot be shining. Maybe if they were pre-christian creationists worshiping a Sun God…

  13. Absolutely true, it is the constant input of the Sun’s energy which makes life on Earth possible. No sun, no life (except, well, maybe you could have some organism using geothermal energy based on gravity).

    However, it does make the initial conditions of the Universe impossible (assuming the Big Bang), as the Universe is presumably a closed system (conservation laws and all that), and we know of no physical process that could lead to the initial conditions. I suppose you could postulate the Universe in connection with other universes (if you want to get rid of the uni-), but that only staves off the problem of the whole, the Meta-verse or whatever you call it.

    1. There is no contradiction between the Second Law and the universe as a closed system. As the universe expands it cools, suns burn out, particles decay, and it ends in an equilibrium “heat death” — a state of maximum entropy and no free energy.

      This may be the most existentially disturbing consequence of the Second Law.

      1. There is nothing wrong with the Universe as a closed system at all.

        The issue is that the initial conditions of the universe are impossible, they cannot be manufactured or replicated by any known physical process. Heat death is not a problem at all, the question is why aren’t we in a static state of heat death, since all known physical processes go from low entropy to high entropy.

        1. Some of us just find Virgin Births hard to swallow, but a Virgin Birth seems more possible than the initial conditions of the universe. . . a sperm introduced outside the hymen leading to pregnancy, or some weird mutation in the mother with an egg that acts as the functional equivalent of a sperm. . . possible but unlikely, whereas our initial conditions are physically impossible.

  14. The interesting issue is the difference between a cipher and a code.

    A cipher provides rules for symbolic transformation (A –> Z or U –> T). It is independent of the meaning of the symbols.

    In contrast, a code transforms based on meaning, “tea” = “marijuana”. Language translation involves decoding a foreign language. It can only be done with some kind of primitive equivalences (like the Rosetta Stone) into a language you can understand.

    Note that a code presupposes an existing system of meaning that the would-be translator understands. Likewise, a cipher, while not being a language, requires language fluency in order for a person to be able to do something with the deciphered message (see Poe’s Gold Bug story).

    The interesting question is whether microbiology will ultimately reveal whether the production of useful proteins from DNA is an example of a cipher or is there a true genetic code, e.g. genetics are symbolic forms of a system of meaning akin to language.

    The observable difference between a system of meaning and a system of symbolism is that the same symbols can mean different things in different contexts (“yes”), whereas a symbol will always just be the symbol (“+” -> “a”).

    So does the organism produce the same protein from the same DNA each time, or does it produce different proteins from the same DNA depending on conditions.

    If we have to begin looking at DNA as providing the basis for a system of meaning, not just mechanical cipher rules, then you have something analogous to a language happening below the cellular level, which gets close to the Dembski’s dreaded “complex specified information”.

    The best part is that these questions are all empirical, and we may increasingly find answers to them. Moreover, it seems more and more mathematicians and physicists are starting to look at biological problems, and want precise, formalized theories, not sloppy theories and hand-waving. (How can you have a “theory of the origin of species” when you can’t even agree on what a “species” is? And if a “species” is a useful fiction, then why does it need a non-fictional theory of origins?)

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