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ORGANIC EVOLUTION 



historical hypothesis, but because of the 

 dominance of the special-creation doctrine 

 they are unknown to us. By the seventeenth 

 century social sanctions relaxed somewhat, 

 and it was then tliat historical descent 

 gradually became a topic for open discus- 

 sion. Some of the men who were bold 

 enough to speak and write their thoughts 

 were Hooke (1635-1703) and Ray (1627- 

 1705) of England, de Maillet (1645-1738) 

 and Buffon (1707-1788) of France, and fi- 

 nally Erasmus Darwin (1731-1802) again 

 of England, the grandfather of Charles 

 Darwin, of whom we shall hear much more 

 later. While all of these men considered 

 evolution as the most likely explanation of 

 animal life on earth, they did not succeed 

 in establishing this principle to any appre- 

 ciable extent because of the scanty facts 

 they were able to muster in support of their 

 thesis. Furthermore, opposition from theo- 

 logians carried such staggering weight that 

 the world gave scant attention to the strug- 

 gling historical hypothesis. But the seed 

 had been sown, and it could not help but 

 gather support as more and more knowl- 

 edge of the natural world accumulated. 

 Moreover, as those who proclaimed evolu- 

 tion began adding theories as to how evolu- 

 tion occurred, more attention and often 

 more support were given to the budding 

 principle. 



Among the outstanding men of this 

 period who pushed tlie doctrine of evolu- 

 tion farther than most was Lamarck ( 1744- 

 1829), a French biologist, who not only ac- 

 cepted the theory of evolution as an expla- 

 nation of the existence of all living things 

 but also proposed a theory which seemed 

 to explain evolution very well. Lamarck 

 was a vitalist, as were the majority of eight- 

 eenth-century biologists. He believed that 

 all living things are endowed with a vital 

 force, distinguished from a physical force, 

 that controls the function of all their parts 

 and ultimately makes it possible for them 

 to inhabit the environment where they now 



reside. Furthermore, he believed that anv 

 traits acquired in the lifetime of an organ- 

 ism were transmitted to succeeding genera- 

 tions. Any such acquired traits could be 

 enhanced or depressed by "use and disuse," 

 that is, the more an organ or part was used 

 the better suited it became to do the job. 

 Such acquired advantages would then be 

 passed on to the offspring. He used the now 

 classical example of the giraffe's neck, in 

 which he assumed that the ancestor of this 

 animal possessed a short neck but because 

 it began browsing on tree leaves and twigs 

 a long neck was particularly advantageous 

 in survival. Hence the continuous stretch- 

 ing of the neck brought about a longer 

 neck, which trait was then passed on to 

 the offspring whose necks would thus be 

 longer. This is a captivating idea and was 

 readily acclaimed by many as the ideal 

 answer to the question as to how evolution 

 occurred. 



Lamarck's theory was the outcome of 

 much thought about the problems that 

 must be solved, namely, random and ori- 

 ented evolution. He knew that a general 



o 



theory, if it were tenable, must explain 

 both. In addition, the great problem of 

 adaptation must occupy the center of the 

 stage in any explanation, because it was at 

 that time and for many years later the most 

 difficult to interpret. His theory encom- 

 passes these features in a manner that would 

 be completely satisfactory if his major 

 premise could be borne out by fact. It has 

 been thoroughly established that acquired 

 characters cannot be transmitted because 

 they do not influence the genes which are 

 the only means of reaching from one gen- 

 eration to the next. Any traits acquired in 

 the lifetime of an individual influence only 

 his soma cells and have no effect on the 

 germ cells. Thus the very heart of La- 

 marck's theory is faulty. Since genetics has 

 firmly established this fact, his theory has 

 no following among modern biologists. In 

 spite of Lamarck's failure, his ideas were 



