154 SECTIONAL ADDRESSES. 



instance, it is essential to make allowance on the one hand for functional 

 necessities, and on the other for the compulsion of material. The more 

 coercive have been the influences of these two kinds, the more necessary 

 is it to seek for minor difierences which have been produced by the free 

 action of variation. 



This brief discussion of the significance of form, as distinct from 

 construction, leads us only to the conclusion that there are no criteria 

 of an absolute character which can be applied to decide a case for 

 or against independent evolution ; only by close comparison and , 

 analysis of every case on its own merits can we justify our faith. It 

 remains true, however, that there is overwhelming evidence to prove 

 that the normal result of independent variation in form is diversity 

 and not similarity. 



A factor in material evolution which is usually recognised, but perhaps 

 also usually underestimated, is substitution or translation. We may note 

 in passing that substitution may be dictated by scarcity or absence of a 

 material that has been commonly employed, or by a chance discovery 

 that one material may be advantageously substituted for another, or that 

 it may occur as a result of search for better materials. The first two 

 reasons are clearly those which must have predominated in early days, 

 whilst the last became operative only under conditions of experimental 

 research — conditions which no doubt prevailed in some degree whenever 

 well-fed communities developed wealth and leisure. Prosperity, not need, 

 is the mother of invention, or at least the fairy god-mother. From our 

 point of view the importance of substitution lay in its power as a factor 

 in discovery and invention through the opportunist reaction of man to 

 the ideas that came to him unsought. In employing a new material for 

 old purposes, it is clear that the preliminary step would be a recognition 

 of sufficient similarity to suggest the possibility of substitution. The 

 endeavour to treat the new material in the same way as the old would 

 inevitably in many cases lead to the discovery that it reacted in a different 

 way, and a new line of evolution was opened up. This is sufiiciently 

 obvious in perhaps the most important of all substitutions — that of 

 metal for stone. The result was not merely the production of better tools 

 and weapons, but an expansion of man's knowledge which gave him a 

 new insight into the possibilities of the raw materials of his environment. 

 It is not too much to say that substitution has been a fundamental factor 

 in discovery and invention from the earliest times, but it must be 

 emphasised that coincidence in a particular substitution cannot be claimed 

 as independent invention. 



If a primary mutation was due to one or more discoveries made in 

 relation to the behaviour of natural objects or materials, it is not un- 

 reasonable to suppose that similar discoveries concerning artefacts may 

 have led to other mutations. As a hypothetical case let us consider the 

 origin of the bamboo spear-thrower of New Guinea, which has a socket 

 for the spear in place of the peg that is present on almost all other spear- 

 throwers. We may suppose that this implement was derived from the 

 ordinary type made of wood, such as is in common use in Australia, and 

 that the first change was that of translation into bamboo. The carved 

 or attached peg for the spear was at first retained, but during the manu- 

 facture or use of the appliance it would be easy for the discovery to be 



