The Second Law of Thermodynamics and Evolution


Proponents of Creationism (and Intelligent Design, which is a sanitized version of Creationism) attempt to use the Second Law of Thermodynamics as a scientific argument against the validity of Evolution. Unfortunately their argument is fundamentally flawed, in that its proponents try to use it without understanding what the Second Law of Thermodynamics really says, or what its implications are. Sadly this erroneous argument is believed by many who read it, who see it as being somehow "scientific", but who do not know sufficient science to realize that it is completely wrong.

The argument (as far as it goes)

  1. Man is a complex organism
  2. Complexity implies a great deal of order, the opposite of disorder, and so a state of lower entropy than existed when the atoms existed in a random disordered state.
  3. The Second Law states that entropy will always tend to increase.
  4. The second and third points are inconsistent
  5. Evolution cannot be responsible for the emergence of complex organisms
  6. Therefore there must be a Creator.
Sounds good, doesn't it. Problem is, it is rubbish, borne out of ignorance about the correct application of the Second Law of Thermodynamics

What is wrong with the argument?

Not much, just the omission of a very important phrase "For an isolated system, . . . ." in the statement of the Second Law. That doesn't seem much, especially to someone who is not informed enough to appreciate the subtleties of the science, but it is enough to completely invalidate the argument in favor of creation mythology.
An isolated system is any one which does not interact at all with its surroundings, either through the exchange of energy or by doing work. The creationist does not seem to realize (or chooses to ignore) the fact that the Earth is not an isolated system, it is not even close to being an isolated system. We receive a tremendous amount of energy from the Sun, more than enough to provide the energy needed to organize simple molecules into more complex ones. Even though this does indeed to a lowering of the entropy on the Earth, the drop is more than compensated for by the huge increase in entropy of the Sun. Conclusion - the Second Law of Thermodynamics does not in any way prohibit Evolution.

Entropy decrease in other non-isolated systems

Evolution of a complex organism is not the only example of a system whose entropy can be made to decrease because of the influence of an external agency. There are countless other examples. Here are a few.


There are countless examples in which the entropy of one region decreases quite naturally. There is nothing whatsoever in the Second Law of Thermodynamics to prevent this. It does not require that the entropy must decrease, unless the region is truly isolated. Providing an outside agency can provide the requisite energy, decreases in entropy are perfectly permitted, as with the case of evolution. The Second Law of Thermodynamics is no way prohibits the process of Evolution.

Another misconception about evolution

Uninformed opponents frequently talk with some disdain about the 'Theory of Evolution' as if it is an unsupported idea. The (perhaps understandable) error arises from a difference in the use of the word theory in science as opposed to its common usage. In science an unsupported idea is more accurately termed an hypotheses. The word theory is used to describe a possible explanation of a well documented observation. For example, we might talk about Newton's Theory of Gravity as an explanation of what gravity is. But in the end it wouldn't really matter if Newton's theory was wrong (it is in fact an approximation), apples will still fall down from trees.
The same is true of evolution. We do have Darwin's Theory of Evolution, as an explanation of how evolution proceeds (by natural selection.) There are other alternative theories also. But even if Darwin's theory (explanation) is wrong, even if all our current theories are wrong, evolution itself is well supported by experimental evidence.

(1) Thor, Nordic god of Thunder
(2) Van der Graaf Generator, a laboratory device for producing high voltages using the separation and storage of electric charges.
(3) First add water, and dissolve the salt. Filter the water to remove the sand (which does not dissolve in water). Last, evaporate off the water.
(4) There are some plants (for example fungi) which use chemical energy rather than sunlight.