Time's Arrow and Evolution

Dr. Blum's main thesis in this small volume is that from the origin of life, evolution has proceeded necessarily along certain channels, predetermined from without by the physical nature of the inorganic earth and by thermodynamic considerations from within. His interpretation of the free energy changes in biochemical reactions is particularly lucid. The exposition draws freely from the disciplines of cosmogony, physical and photochemistry, to name a few. There is no denial of the importance of natural selection as an evolutionary force, but rather a setting of limits within which this force may operate. The title suggests an attempt at explanation of the mechanism of evolution on the basis of the second law of thermodynamics. No such explanation is presented. However, the ghost of "living systems being a contradiction of the second law" is forcefully laid by emphasizing the requirement of a closed system for measurements. The living organism is not a closed system, nor is the earth which it inhabits. In order for life to constitute a violation of this law, it must be proven that the local decrease in entropy in the living thing is not compensated for by greater increases elsewhere in the same system. The text in general is clearly written and self-explanatory, demanding little technical training of the reader. Particularly stimulating are the chapters entitled, "The Fitness of the Environment" and "The Origin of Life." W. P. McN.