Evolutionary Process From Chaos to Order

Recently a group of biologists, physicists, astronomers, and philosophers met at California State University, Fullerton, to discuss the relation between biological evolution and the physical sciences. The speakers all agreed as to the reality and importance of evolution. Beyond that, they had little in common except dislike for the pattern of views that has constituted the mainstream of evolutionary thought in recent decades, which is sometimes called neo-Darwinism. No representative of those views was present.

My comment is important for understanding of the issues. A report in The Times asserts that “The second law of thermodynamics says that systems by their nature break down into disorder. Yet biological organisms have evolved in the opposite direction.” If the second law actually said that it would be incorrect; systems of very many kinds change toward states of greater order. That in fact is the usual, although not universal, tendency for systems generally. A star is much more ordered than the hydrogen cloud from which it formed.

In the May, 1985, issue of Scientific American, Hans Bethe, who received a Nobel Prize for his study of nuclear processes in stars, and a colleague point out that “the entire evolution of the star is toward a condition of greater order.” Gravitational attraction causes condensation of dispersed hydrogen into a compact mass; nuclear-fusion reactions convert hydrogen into helium. In this process, four disordered atoms of hydrogen have gained order by becoming bound together to form an atom of helium. Some of the matter in helium becomes more ordered by being converted to heavier elements whose nuclei are ordered arrangements of a larger number of nucleons derived from hydrogen atoms.

Order increases also in the evolution of a planet. A disperse cloud of gas and dust was converted, for example, into the Earth, which is differentiated into a metallic core, a mantle, and a continental crust of lighter material floating at the surface. This process of increasing order continues with the development of the high degree of chemical and topographic order that characterizes the surface of the Earth. It also continues, with the addition of specifically biological factors (selection from among random mutations), right up to our own highly ordered bodies.


These pervasive increases in the order of systems can be conceptually balanced against energy lost to the surroundings in the form of heat, electromagnetic radiation, or neutrinos. That is one application of the second law of thermodynamics, and in many contexts in physics, chemistry, and astronomy it is important. But when we are interested in a system itself, such as a planet, a rock, a tree, or an animal, the important point is its high degree of order, not what may have happened to the rest of the universe during its past history.

In becoming more ordered with time, living organisms are not reversing the direction of change that occurs in non-living systems; the processes of biological evolution (mutation and selection) accelerate and in a sense direct the same change toward greater order that is characteristic of nearly all the systems, non-living as well as living, that we see around us.

The misconception that non-living systems go toward disorder (has anyone seen a planet revert to a cloud of gas and dust?) whereas organisms proceed toward order is responsible for such misunderstanding of the meaning and significance of evolution.



Professor of Biochemistry

University of California,

Los Angeles