Building Stones to a Chemistry of Evolution

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Abstract
All deductions are based on the assumption that evolution depends largely upon the formation of new types of hereditary units, e.g., genes. They can be formed only by chemical reactions, and consequently should be produced according to the laws of chemistry. While the actual reagents involved are unknown, some general laws can be applied successfully, and statistical evidence seems to justify the following statements : The frequency of the creation of a new hereditary unit in any given species is proportional to the number of individuals bom per year. This is made probable by a survey of the plants of North America among which the rare families have few species while the common families have many spp. The frequency of the creation of a new hereditary unit in any given species is greater in warmer climates because chemical reactions proceed more rapidly at higher temps. This is borne out by the evidence that among reptiles, there are about 8 times as many species in tropical climates as in moderate climates while with mammals whose reaction temp. is constant the ratio is only 2:1. The number of species of plants also increases with the temp. of the country. This evidence indicates further that the formation of new hereditary units is not caused by cosmic rays or any other kind of radiation because the rate of reactions which are caused by radiation is independent of the temp., and statistical evidence shows a dependence. Polyploidy is probably not caused by chemical reactions, for it shows no relation to the number of spp. existing, nor does it increase with temp. A change of environment is likely to affect cell chemistry, and to induce new reactions which might lead to the formation of new hereditary units. The frequency of such reactions should be proportional to the frequency of environmental changes. This is largely a question of size. Some microscopic organisms may change their environment daily on an enormous scale, e.g., intestinal or soil micro-organisms. Variation in bacteria is so common that in several groups, species definitions are arbitrary because all shades of intermediate forms between any 2 "established" spp. have been described.