26 PHYSICAL BASIS OF CIVILIZATION 



towards the diaphragm, but the upright attitude 

 interferes with their doing this service in the case of 

 human females, which accounts for the frequency in 

 our race of painful and dangerous illness from pro- 

 lapsus and various other displacements of the uterus. 

 The same position and shape of the pelvic bones 

 which makes parturition easy and painless in quad- 

 rupeds becomes in the human race the prolific cause 

 of suffering and death to mothers and offspring. 



The immediate progenitors of the upright brute 

 ancestors of man must have resembled the quad- 

 rumana. These latter were descended or were 

 derived from quadrupeds. Among these latter the 

 horizontal attitude on all fours has been normal 

 since unnumbered generations and variations have 

 been naturally selected, during all this enormously 

 long period with reference to their adaptation to this 

 position. 



Form and location of blood-vessels, of the valves 

 in them, of the viscera, of the reproductive organs, 

 etc., and of the bones, ligaments, muscles, tissues, 

 which protect, support, and connect these parts, have 

 slowly through the ages become beautifully adjusted 

 to the position of the body on all fours. 



The occurrence thereafter by variation through 

 sexual reproduction of two slight anatomical modi- 

 fications, whose nature and effects will be more fully 

 discussed hereafter, forced our brute ancestors to 

 abandon the horizontal and adopt the upright 

 attitude. The advantages of the adjustments and 



