274 THE EVOLUTIONARY CAREER 



uranium and radium atoms, but it may be regarded as going on, 

 very much more slowly, in all kinds of atoms. In the course of 

 these changes the bound energy of the atoms is liberated as high- 

 frequency radiation, but this suffers dissipation by absorption into 

 other substances and ultimately it transforms into the low- 

 frequency radiation of heat and tends to become uniformly distri- 

 buted throughout cosmic space. 



And thus the materials and energies that constitute the stars, 

 cooling and shrinking planets and chemical substances tend always 

 from states in which these elements (the materials and energies) 

 are concentrated, or are arranged in improbable configurations, 

 towards states in which the concentrations are levelled out, or 

 in which the elements become arranged in the most probable 

 configurations. These tendencies of inorganic evolution are 

 clearly illustrated, in a trivial way, of course, by the disappearance 

 of the configuration of a Patience card-series, when shuffling is 

 carried out. 



An important result : In all inorganic evolutionary processes 

 the probability of the arrangements of the partSy or elements, of the 

 system concerned increases. Now it can be shown that the entropy 

 of the system must increase as the logarithm of the probability 

 increases. 



90. ON THE TENDENCY OF ORGANIC EVOLUTION 

 First we shall consider the formation of the " biosphere," that 

 is, the concentric layer of living organisms inhabiting the soil, 

 ocean and fresh waters, and atmosphere (that is, the lithosphere, 

 hydrosphere and atmosphere). As to the origin of living things 

 on the earth we know nothing. It is simplest to assume that, 

 just as the primary vapours of the planetary mass fell together, 

 condensed and chemically transformed themselves into the litho- 

 sphere and hydrosphere, so other vaporous constituents fell 

 together and reacted chemically with the materials of the other 

 envelopes so as to form the biosphere — that is, the first living 

 organisms capable of reproduction. The difficulties of such an 

 assumption are overwhelming, but it has been customary to make 

 it and for the moment we accept it. The earth, then, became 

 populated with simple organisms of the same kind, at some period 

 of about 1,500 to 1,000 millions of years ago. It is the simplest 



