53,^ 



The Journal of Heredity 



manmals, among; whom "friends, and 

 food, are found by their scent; foe are 

 avoided by the same sense, and the 

 whole sexual life of the animal is lived 

 in a like atmoshpere." But when Man's 

 ancestor's took to the trees, the sense 

 of smell became of less importance, for 

 no trail of scent is left among the trees 

 as it is on the ground. The uselessness 

 of the sense of smell opened the way for 

 the development of the other senses, 

 and of other parts of the brain, to the 

 great degree in which Man now shows 

 them. Nevertheless, this primeval sense 

 which in modern man is none too well 

 de\-elopcd and is a very minor factor in 

 his life, "still shows a subtle power as a 

 memory sense. Dudley Kidd has noted 

 this feature in invc-ligating the psychol- 

 ogv of Kafir children. 'When Kafirs 

 are questioned as to their earliest re- 

 membered impressions they usually 

 state that these w-ere connected with 

 the senses of taste and smell. The next 

 things they remember are connected 

 with the sense of color; then impres- 

 sions of sound and of form seem to 

 follow last of all.' In still more primitive 

 races the importance of smell impres- 

 sions is probably greater; and there are 

 few of us who have not some complex 

 memory picture associated with an 

 early impression of smell." 



THK SENSE OF TOUCH 



The sense of touch was likewise 

 modified by arboreal life, coming to 

 be centered largely in the hand. This 

 helped emancipate the animal from its 

 domination by the sense of smell, and 

 it contributed to the development of 

 new areas in the brain. 



The evolution is evidently harmoni- 

 ous in its details. The more the fore- 

 limb becomes emancipated, the less 

 is the hand called upon for menial duties 

 which in other stocks necessitate the 

 de\elo]jment of skin-thickenings, pads, 

 callosities, or hoofs. It is the freed 

 hand which is pennitted to become the 

 sensitive hand, and it is the freed and 

 sensitive hand which now, so to speak, 

 goes in advance of the animal and feels 

 its way as it climl)S through life. The 

 animal no longer smells out an object 

 subsequently to feel it with its nose: 



but it feels with its hand some object 

 that comes within its reach in the cus- 

 tomary round of arboreal activities, 

 and it may or may not subsequently 

 add to its knowledge of the object by 

 smelling of it. Tactile impressions 

 gained through the hand are, therefore, 

 constantly streaming into the brain of 

 an arboreal animal, and new avenues 

 of learning about its surroundings are 

 being opened up as additions to the 

 old olfactory and snout-tactile routes. 

 With the development of the power of 

 grasp, new and great possibilities come 

 in. Much may be learned of an object 

 that can be felt by the hand; much 

 more of an object that can be grasped, 

 lifted and examined in the hands. 

 When an object can be grasped and 

 lifted it can be examined from every 

 point of view, and the eyes must play 

 a large part in this examination. Its 

 whole outline, the texture of its sur- 

 face, its hardness or softness, its size, 

 temperature, and weight, can all be 

 ascertained. It is difficult for us, with 

 our ]3erfected cerebration, to appreci- 

 ate the difference which the power to 

 gras]) an object makes to an animal 

 attempting to learn the nature of 

 objects with which it comes in con- 

 tact, but we may be sure that the 

 difference was very great, and was 

 made greater when the power to pick 

 up the object and to examine it from 

 all i)oints of view was added. 



HIGHER MENTAL FUNCTIONS 



It is even possible, Professor Wood 

 Jones thinks, to connect the evolution 

 of higher mental functions with the 

 arboreal life of man's ancestors; to find 

 a partial clue to the origin of those 

 "higher ideals of conduct" which some 

 critics have alleged could not possibly 

 be exi)lained on an evolutionary basis. 



It has already been j^ointed out that 

 arboreal life leads to a reduction of 

 the number of young produced at a 

 birth. This is, of course, a mere adap- 

 tation to life circumstances, and is not 

 confined to the Primates but will occur 

 where\-er there is no natural nursery 

 for the young. If the tree-dwelling ape 

 has but a single young at a birth (as a 

 rule), so do the horse and the whale. 



