THE EVOLUTION OF MAN 99 



can do no more on the way in which the lemur 

 evolved into a man during the Tertiary period. How it 

 shed its tail is a trifle: the anthropoid ape also has 

 achieved this. Possibly the fusing of the sacral vertebrae 

 to form a solid support for the more or less upright form 

 led to the degeneration of the rest of the column. The 

 centre of interest is this adoption of an upright posture, 

 for this is probably one of the chief keys to man's 

 higher development. There is little mystery about the 

 adoption of this posture in itself. In a tree-climbing 

 animal it comes not unnaturally. The gibbon stands 

 quite erect, and the other anthropoid apes more or less 

 throw the weight on the hind limbs ; while the Pithecan- 

 thropus shows that the habit came gradually. In the 

 fierce struggles against the increasing carnivores on the 

 Tertiary plains the horse, antelope, etc., found their 

 safety in speed. The ape took to the trees, and the 

 strength and tenacity of the new-born baby's fingers 

 recall our own arboreal ancestor. The baby can support 

 itself by hanging on to a stick. Dr. Robinson found that 

 some babies under a month old could support themselves 

 in this way for more than two minutes. 



It is thought by many authorities that this tree- 

 climbing habit, by leading gradually to the adoption of 

 an upright posture, was the chief determining agency 

 in the initial development of man's intelligence. Any 

 good work on physiology (I have Kirk's before me) will 

 show that the hand-centre in the brain verges upon the 

 region which is now known to be instrumental in acts of 

 reason. Hence any important advance in the use of the 

 fore-extremity will develop the hand-centre in the brain, 

 and may stimulate the neighbouring intelligence-centre. 

 Now the adoption of the upright posture involved a 

 change of this character. Instead of a passive support 

 to the body, the fore-foot becomes a hand with prehensile 



