September, 1928 



EVOLUTION 



Page Three 



P'or America needs 66% of the world's rubber, but 

 controls only 2V2% of the rubber plantations; so keen 

 and desperate is the rivalry for rubber that it may be- 

 come one of the causes of a great war; to produce rub- 

 ber is now a national necessity. So we may be sure 

 that the hard-headed managers of a great corporation 

 and the hard-headed Dr. MacCallum whom they employ 

 are not working by any empty theory. They are not 

 guided by feelings about philosophy or tiieology. They 

 are strenuously trying to get hold of more rubber by 

 methods that are most likely to secure results. 



Dr. MacCallum's method is the basic principle of 

 evolution, and the steps of his work illustrate one line 

 of proof of that theory. He believes in evolution as 

 thoroughly as a cotton-grower believes in rain; and he 

 knows that an enemy of evolution is an enemy of indus- 

 try and civilization and horse sense. 



In the first place, he knows — as every farmer knows 

 — that a young rubber plant will be very much like its 

 parents. It will inherit all their trails of forming roots 

 and leaves and filling its tissues with a rubber that can 

 be made into Ford tires. This is the principle of "hered- 

 ity." It is no more theoretical than a rubber tire. Off- 

 spring tend to resemble their parents. 



But Dr. MacCallum also knows that no young plant 

 ever resembles its parents completely. Ii may have been 

 a trifle speedier in sprouting from its seed; it may be 

 slightly more able to withstand drought; it may be some- 

 what more able to endure a cold summer; its fibers may 

 contain a higher percentage of rubber. Every plant 

 and animal varies to some extent from being an e.xact 

 duplicate of its parents. This is the principle of "varia- 

 tion." It is no more a theory than a steering-gear is. 



For fourteen years Dr. MacCallum has been busy 

 selecting those shrubs that have varied in ways which 

 will make them more profitable as domesticated plants. 

 First he selected from a bewildering lot of wild varieties 

 the few that were most promising. Then from the off- 

 spring of these he selected the variations that tended to 

 sprout and develop at the times that are best fitted for 



Texas and California farming. Of course he discarded 

 all rubber plants that were varying in the direction of 

 producing less rubber. By saving the right variations 

 and discarding the wrong ones he was gradually pro- 

 ducing the sort of plant that can furnish automobile 

 tires. For the selected variations are preserved and 

 transmitted by heredity to succeeding generations. This 

 IS the principle of "selection." It is no more iheorelical 

 !han the price you will have to pay for an inner lube 

 if the United States cannot grow its own rubber. 



All breeders of plants and animals have known for 

 centuries this method of selecting favorable variations 

 and building up what is useful to man. It is the process 

 which has given us the valuable varieties of wheat, corn, 

 roses, cattle, horses, and fowls. There is not a farmer 

 in the United States who thinks that this process of 

 breeding by selection is untrue. Every farmer knows 

 that selection is the foundation of modern agriculture. 



Darwin wondered whether there might not be in nature 

 a process similar to this artificial one. He knew that 

 some variations must help a plant or animal to do bet- 

 ter in the struggle for existence, and that some variations 

 must be unfavorable and cause it to die. "May it not 

 be," he wondered, "that the conditions of life are always 

 killing off unfavorable variations and allowing only the 

 favorable ones to multiply?" If this was the case, then 

 the forces of nature would always be tending to preserve 

 variations in certain directions and to kill them off in 

 other directions. If nature had operated thus over very 

 long periods of time-^millions of years — it might grad- 

 ually have caused an animal to become vastly different 

 from its remote ancestors. Perhaps all the millions of 

 varieties of plants and animals had been produced by 

 this sort of evolution. 



Darwin did not fall in love with his new theory just 

 because it looked pretty. IN or would scientists ever have 

 accepted it jusi because it seemed probable. Evolution 

 would have remained a mere guess if no other kinds 

 of evidence liad been discovered. The other kinds will 

 be described in the next two articles. 



McGregor Reconstructs Ancient Man 



By Allan Strong Broms 



"IN the Hall of the Age INIaa in the American Museum of Natural 

 History are several busts of prehistoric races of man. They 

 have been modeled by Dr. J. H. McGregor, Professor of Zoology 

 at Columbia University and Research Associate in Human Anat- 

 omy at the Museum. This means that they are the best racial 

 portraits our present knowledge permits, for Dr. McGregor is 

 a careful and skilled sculptor-anatomist and devoted a good part 

 of five years to the making of these likenesses of the ancient 

 races of mankind. This was no mere work of artistic imagination, 

 but a task of scientific accuracy done by the man who has made 

 himself the world's foremost authority in his field. 



Our cover this month shows his reconstruction of Neanderthal 

 man, whose race lived in Eurnpe some twenty-five to seventy- 

 five thousand years ago. He told the story of its making. For 

 a start, he had plaster casts of many fragments, several fine jaws 

 and seven fossil skulls upon which to base it. Tlie skull of La 

 Chapellc-aux-Sainls, France, which had proved to be most com 



plete when pieced together, was used as the base for this par- 

 ticular head. As the original fossils, besides all being in Euro- 

 pean museums, were much too delicate and valuable, plaster 

 casts were used throughout the work. 



The first job was to restore the missing teeth and nasal bones 

 by comparing similar parts from kindred remains, making them 

 over, of course, to fit the parts that were intact. The hole in 

 the skull was readily filled by using the other half as a model. 

 On this nearly perfect cast was then modeled the fleshly form. 

 With his other duties, this took him one whole year, so exacting 

 was the work. 



The ne.\t step was to model the neck. Its fossil bones were 

 available as a guide and were carefully drawn full size in vertical 

 section. The other vital parts, muscles, ligaments and organs. 

 were then filled in as exactly as possible and upon this basis 

 the outer form was built. The skull was then poised on this 

 reconstructed neck in its natural position. The neck proved 



