1044 EVOLUTIONAL MODIFICATIONS 



took origin, to tliat stock w liicli ma\ he traced, as Huxley and others main- 

 tain, to the organization of some lo\\l\' mammal such as thc' tree-shrew 

 (tupaia). Nor is there reason to pause at this point in the long hue ol descent. 

 Looking still furtlier back into the ]3ast, it is possible to recognize those 

 premammalian reptiles from which tlu' mammals uncjuestionably descended, 

 as well as their progenitors deri\ed Irom those low Ie\els ol xertebratc 

 organization which gave rise to the great Mesozoic reptilian orders. 

 It is indeed the a]i])reciation of this long ancestral line in all the \arious 

 modifications ol its many geological phases that gives the proper \ahie to 

 the e\'olutionarv process. Perceived in this way, it is possible to sense the 

 lull force ol the impetus in that irresistible momentum w hich has carried the 

 great vertebrate ph\ lum upward and onward through the ages and may still 

 carry us onward. 



This is a conception that should make an urgent appeal for thoughtful 

 consideration regarding lurther possible readiustment ot human behavior. 

 It is a ^•Iew■ ol lite which requires lor its acceptance real powers ot vision 

 combined with an open attitude ot mind. For now, as in the past, intolerance 

 may resist as rude intrusion any trespass upon its ancient and cherished 

 delusions, preiudice may reject as worthless what it has not itscll conceixed 

 as true, conservatism may urge a wai"\ hesitation m the acce]:)tanee ol broad 

 conclusions ol an\ kind. But these facts, corrt'lated here, perhaps tor the first 

 time, and standing alone w ithout the aid ol eommentarv or special interpreter, 

 speak in no uncertain terms of a structural iintoldmg in the brain ol primates 

 whose e\'olutional signilicance may be seen in the progressne extension ol 

 their behavioral ca])acities. In this as])ect these factors may appear merely 

 as a conventional formulation of scieiitilic deductions. They may fail entirely 

 to create an impression of the actual dxnamii- force which lies behind tlu'in. 

 It is for this reason and by \ iiiiu' of ha\ ing essa\ ed to aiisw er so maii\ (|u cries, 



