GENETICS — STERN 269 



environment of a forest or a meadow is evidence of the existence of 

 thousands of occupied ecological niches, and surely of many more yet 

 unexplored. Sometimes the new assemblage will happen to survive 

 in a changing environment where the original assemblage was doomed 

 to extinction. The "deterioration of the environment," so-called by 

 unadjustable men, is a continuous process; for the flexible, environ- 

 mental change is a challenge to inventiveness. 



Let us, however, not be deceived by this anthropomorphic phrase- 

 ology. It fits our discussion in a figurative manner, but only in a 

 most indirect way does the genetic model of evolution provide an 

 organism with attributes of unadjustability or inventiveness. 

 Changes at the molecular level all too often happen not to be adjusted 

 to the demands of a higher level. Occasionally they do. The wonder 

 is that for two billion years the genes have succeeded in escaping 

 extinction. They survived, that is, left duplicates when they hap- 

 pened to clothe themselves in lambs and lions, amebae and bacteria, 

 algae and oak trees, tapeworms and men. They perished when they 

 were trapped within trilobites and dinosaurs, or within the tree ferns 

 and giant horsetails of the carbon ages. The genetic view of evolu- 

 tion may be expressed in a variation of a well-known sentence : All 

 living forms are only the genes' ways of making other genes. 



Not that the genes could escape the process of evolution themselves. 

 In order to create the superstructures of animals and plants within 

 which to survive, the genes had to change themselves. Single, sepa- 

 rately existing genes at the dawn of life had to become associated into 

 harmoniously fitting groups ; mutations of the genes had to make pos- 

 sible the development of the manifoldness of organisms. The one 

 prerequisite invariant in the evolution of the gene had to be its prop- 

 erty of reproducibility. What else remained constant we can only 

 guess — perhaps protein or nucleic acid structure, taken in a general 

 sense; perhaps enzymatic property. The evolution of the gene, as 

 gene, is a field of inquiry barely touched. 



This then is genetics as a way of interpreting living nature. This is 

 Mendelism — ^Weismannism — Morganism — Mullerism — Goldschmidt- 

 ism — Beadleism — Haldaneism — Fisherism — ^Wrightism. This is the 

 framework which our times have built. It has been called "idealistic" 

 by those to whom this term is one of condemnation, and with equal 

 reproach has been termed "materialistic" by their opponents. 



The new view of biology which genetics has provided may seem 

 to many a denaturation of nature. Instead of birds with beautiful 

 feathers and sweet songs, with artful nests and loving care of the 

 young, we speak of the gene molecules which control pigmentation 

 reactions and the deposition of cartilages in the singing box, deter- 

 mine the architecture and physiology of the brain, and the hormonal 

 secretion of the pituitary gland. But the molecular interpretation 



