182 E. J. Salisbury 
lithic period given place to the hafted axe on the one hand and the 
spear-hea‘d, arrow-head, etc. on the other, all of which attained a 
much higher development in the Neolithic period. 
To the biologist the implements of the Stone age in particular 
and in a lesser degree those of the Bronze and Iron ages are replete 
with examples of the importance in evolution of apparently trivial 
distinctions. As in animate objects, not all of these potentialities 
develop. In the earliest borers of the Chellaean period we find the 
“ heron ” with curved edges which become straight with the improved 
technique and finer baking of the Acheulaean type of borer. Thus a 
potentiality was lost, not to reappear, as a parallel development in 
metal, until quite modern times where the borer with the twisted 
edge finds expression in the high speed twist drill. 
We see the forces of natural selection at work in the Neolithic 
period leading to the sifting out of specialised types in correspondence 
with the changed conditions consequent upon the replacement of 
Palaeolithic Man the hunter by Neolithic Man the agriculturalist. 
The hafted implement attains a high state of development and the 
so called “adze,” probably used as a hoe, makes its appearance. 
With the advent of metal an entirely new factor is introduced. 
It was as it were a profound mutation yet, as with plants and 
animals, the potentialities are not at first obvious and in the initial 
stages the evolutionary continuity appears to be scarcely affected by 
the change. Just as the first motor cars were mere caricatures of 
their horse drawn predecessors, so too the first bronze celts were mere 
replicas in metal of their stone prototypes. 
The bronze axe was bound in the split short arm of the L-shaped 
haft and we find the capabilities of the new material first developed 
in the flange at all four edges, to prevent vertical movements, and 
in the elaboration of the “stop” or transverse ridge which held the 
axe from being driven back into the haft by the force of the blows. 
The final phases of this series are the socketed axe-heads with a 
vertical septum, clearly derived from completely bent-over flanges, 
and finally the socketed celt with no septum and a loop through 
which the binding thongs passed. The latter represents the end of a 
series which has become extinct but the less specialised palstave 
survives in the machete of modern days. 
The chief effect of the introduction of metal is seen in the 
lengthening of the sword blades and in the manufacture of slender 
implements such as pins, needles, etc. The latter made of bone had 
however already appeared in Palaeolithic times and it is doubtful 
