274 THE PRINCIPLES OF HEREDITY 



become feeble, his teeth liable to decay, and his stomach 

 incapable of assimilating the raw coarse food on which his 

 ancestors flourished. 



440. It would be difficult to indicate the most important 

 physical change which accompanied the evolution of man's 

 memory, but certainly none has had results more far-reaching 

 than that which has occurred in his organ of speech, and 

 rendered articulate language possible. Three things must 

 have undergone concurrent evolution, the evolution of any 

 one being impossible without the others the hemispheres of 

 the brain, the organs of speech, and language. The first 

 two are natural endowments of the species, actual physical 

 parts of the individual, wholly inborn in the infant, but with 

 acquirements superadded in the adult. The third is a mere 

 system of signs which man has invented. Almost as complex 

 in its way as the brain, its elaboration must have been nearly 

 as slow as the evolution of the hemispheres. But this system 

 of signs enables him to communicate, and so in succeed- 

 ing generations to accumulate knowledge abstruse, varied, 

 voluminous, complex to a degree immensely beyond anything 

 that could have been achieved without its aid. Lacking it, 

 his great brain, his great power of making mental acquire- 

 ments, would be useless. The knowledge of this great system 

 of signs is in effect, though not in fact, an instinct, since, as 

 an absolute condition of human survival, it has been handed 

 without break by every generation to the next from that 

 remote past when man first emerged from the brute. A 

 single acquirement, it is a superior substitute for many 

 instincts. Owing to the unfailing possession of it by an 

 endless succession of generations, man has regressed so far 

 in structures and instincts that but for language, and all that 

 is communicated by language, he is as unfit for existence as 

 a military ant without its slaves. If for a single generation 

 this all-important system of signs were lost, and man, were 

 it possible, survived, he would at once be reduced to the 

 condition of a brute, and, his equipment of instinct being 

 small, a very helpless brute. His highest faculty, his enor- 

 mous power of making and using mental acquirements, of 

 profiting by experience, would be rendered nugatory. Under 

 the new conditions the fit who survived would not be the 

 same as heretofore. And since the power of acquiring the 

 higher mental faculties would be no longer a principal factor 

 in survival, that power would necessarily regress, and man 

 would degenerate towards that ancestral form in which it 

 did not exist. 



