EVIDENCES— EXISTING ORGANISMS 107 



limitations of human records lose sight of it altogether and we look 

 upon our friends and associates as wholly unrelated. Supposedly 

 unrelated individuals marry. The union of any more closely 

 related than cousins is frowned upon, yet after all these are only 

 degrees of relationship. 



The relationship of these apparently unrelated individuals 

 serves as an excellent illustration of the course of development of 

 a population. Assuming that one individual is produced by un- 

 related parents, and that his parents are derived from equally 

 distinct lines, only a few generations back we find his ancestors 

 multiplied to a ridiculous point. The number of ancestors doubles 

 with each generation in geometrical progression. Allowing twenty- 

 five years to each generation, a reasonal^le average for the period 

 covered by recorded history, we find that seventy-seven genera- 

 tions have passed during the Christian era. By carrjdng the an- 

 cestry of our one individual back through one-half of that period — 

 238 — ^g reach the stupendous total of 274,877,906,944 ancestors. 

 The present population of the world is approximately 1,748,- 

 000,000 and it has increased constantly. Or on the basis of the 

 closest union, that of cousin marriages, assuming even the im- 

 possible constant of siblings marrying cousin siblings, we find that 

 the total ancestry of one hundred unrelated individuals vastly 

 exceeds the total population of the world fifty generations back. 

 The absurdity of these results is ample evidence that all members 

 of a given species are related in some degree. 



By carrying out such computations of ancestry and comparing 

 them with the increasing population of the world, it is obvious 

 that the individuals of any species have sprung from a very 

 limited number within the period of recorded history. It is neither 

 difficult nor illogical to carry the idea back to an initial unit, an 

 individual or pair. Both biologically and through other sources 

 this view becomes available. 



Relationship of Species. As we apply this analysis of relation- 

 ship to the species which make up the organic world, we find that 

 the direct connection of one with another which is evident in indi- 

 vidual relationship is not apparent. The period covered by human 

 records is so brief that it does not afford an opportunity to view 

 the transition of one to another. That this transition may yet 

 be seen is strongly suggested by the production of distinct forms 

 by mutation, a process which will be considered in detail in a later 



