Tuesday, October 14, 2008

Entropy and Evolution

I mentioned quite a while back of the very common abuse of the 2nd law of Thermodynamics by anti-evolution zealots. They claim that evolution contradicts the 2nd law simply because evolution ends towards more ordered (and thus, lower entropy) creatures. This is of course false in more ways than one, and I presented it as an example of "imagination without knowledge is ignorance waiting to happen".

However, not only that, but one can actually show that evolution can be successfully described by the 2nd Law of Thermodynamics. This shows that there's nothing contradictory regarding evolution and the 2nd law. Notice that these creationist zealots never once tried to apply any laws of physics to their own beliefs on how the various living creatures came into being (can we say "violation of the conservation of energy"?).

Along comes a very good article by Dan Styer, published in the latest issue of the American Journal of Physics. Titled "Entropy and Evolution"[1], he tackled very much the same issue.

Abstract: Quantitative estimates of the entropy involved in biological evolution demonstrate that there is no conflict between evolution and the second law of thermodynamics. The calculations are elementary and could be used to enliven the thermodynamics portion of a high school or introductory college physics course.

He basically calculate the change in entropy of the Earth due to evolution:

Presumably the entropy of the Earth’s biosphere is indeed decreasing by a tiny amount due to evolution, and the entropy of the cosmic microwave background is increasing by an even greater amount to compensate for that decrease. But the decrease in entropy required for evolution is so small compared to the entropy throughput that would occur even if the Earth were a dead planet, or if life on Earth were not evolving, that no measurement would ever detect it.

An excellent article to read!


[1] D. Styer, Am. J. Phys. v.76, 1031 (2008).

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