LECTURES IN BIOLOGICAL SCIENCES 



has attempted to understand and control his own nature, that 

 is to say, the systems of religion, philosophy, and politics." 



In his paper Dr. Norman G. Anderson discusses pertinent 

 evidence from astronomy, geology, biochemistry, biophysics, and 

 genetics that suggests the way in which life began on the earth, 

 even how the earth itself came into existence. In this critical 

 review Dr. Anderson proposes several specific lines of experi- 

 mental study needed to fill gaps in our knowledge and to test 

 the validity of several hypotheses that have been proposed. His 

 speculations lead him eventually to consider a problem that 

 especially excites the popular and scientific imagination in this 

 space age, that is, the likelihood of the evolution of intelligent 

 life elsewhere in the universe. Dr. Anderson also speculates 

 about the probable reaction of some early Christian leaders, 

 such as St. Thomas Aquinas, to suggestions that life arose spon- 

 taneously. 



Professor C. H. Waddington reviews the development of 

 population genetics and the implications of the three major 

 concepts that the field has produced: the near universal and 

 unexpectedly great abundance of genetic variation in natural 

 populations; the generally increased fitness of heterozygotes; 

 and the co-adaptation of genes in the gene pool. His considera- 

 tion of the origin of genetic variability and the manner in 

 which natural selection acts upon it leads to a discussion of the 

 role of the environment. Professor Waddington tells of his 

 remarkable discovery of how some environmental modifications 

 that may be adaptive in Drosophila can be selected to produce 

 consistently the adaptive types in subsequent generations in the 

 absence of the environmental conditions that originally induced 

 them. He then contrasts this kind of "acquired trait" with the 

 modifications of an adaptive kind that the Lysenkoists, but not 

 other scientists, suppose can be directly produced by the en- 

 vironment and then transmitted by the organism to its progeny. 



Professor G. Ledyard Stebbins gives examples from a variety 

 of literature to illustrate each of seven basic postulates that be- 

 long to the modern theory of causes of evolution. These sum- 

 marize contemporary thinking about the ways in which, par- 

 ticularly, natural selection, mutation, genetic recombination, 

 and isolation operate and interact in natural populations to 



VI 



