Doesn’t Evolution break the Second Law of Thermodynamics?

No, it doesn’t.

The Second Law of Thermodynamics is one of the most fundamental laws of nature: evolution really would be in big trouble if it contravened it. Put not particularly simply, the Second Law of Thermodynamics states that the entropy (the amount of disorganisation) in a closed system tends to increase with time. Put more simply, this means that matter does not tend to organise itself in a particular location unless there is some external energy source powering it. Evolution can be seen as matter organising itself.

Earth and sun
Earth and a major external power source.

Evolution-deniers who cite the Second Law of Thermodynamics as proof against evolution happening on our planet either conveniently forget to mention, or do not realise, that the earth is not a closed system: it has a rather massive external energy source, namely the sun. If we were to consider the entire solar system to be a closed system (which, to all intents and purposes, it is), then the occurrence of evolution on any of the planets would not break the Second Law of Thermodynamics, because, while evolution represents a local decrease in entropy, the burning of fuel within the sun represents a far greater increase in entropy—so, within the closed system as a whole, there is still an overall increase in entropy.

This is not a case of special pleading on behalf of evolution, by the way: the concept of a closed system is fundamental to the Second Law of Thermodynamics.

Richard Carter, FCD

Writer and photographer Richard Carter, FCD is the founder of the Friends of Charles Darwin. He lives in Hebden Bridge, West Yorkshire.WebsiteNewsletterMastodonetc…


  1. I thin your analysis is off. Hiroshima had a 16 kilotons worth of external energy dumped on it and there was no increase in order. You are confusing entropy with enthalpy.
    The creationist would respond that energy does not increase order in a system it decreases it. He would be right. Unless there is a system in place to use and direct that energy, adding energy increases entropy.

    1. At no point do I say that an energy source is all that is required for order to occur. My point is that Darwinian evolution does not break the Second Law of Thermodynamics as, in the Earth-Sun system as a whole, entropy still increases.

  2. Actually, increasing the energy of a system will increase the entropy. What makes a reduction in entropy possible in a non isolated system is not that energy can enter but that it can leave. Consider the freezing of water. Water freezes to form ice which is lower in entropy than liquid water. This entropy reduction is compensate for by the increase in entropy of the surroundings due to the release of latent heat, thus satisfying the 2nd law. The same is true of the sun. In the sun's core hydrogen is being converted to helium with a resulting decrease in entropy. But the release of heat into space increases the entropy of the universe in general so again the second law is satisfied. Living organisms grow and evolve which involves a decrease in entropy, but release heat and high entropy waste products into the environment in accordance with thermodynamics

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