1903 - 4 .] Dr Munro on Man in the Palaeolithic Period. 95 
of the alveolar ridges and the consequent more upright setting of 
the teeth in their sockets. But whatever the precise cause may 
have been, there can be no doubt that the gradual formation of 
the chin has a striking parallelism with the progressive stages 
of man’s intellectual development, ever since he diverged from the 
common stem line from which he and the anthropoid apes have 
descended (see fig. 18). 
From these general remarks it will be seen that there are two 
distinct lines on which investigations into the past history of man- 
kind may be profitably conducted, both of which start from the 
attainment of the erect attitude. The evidential materials to be 
gathered from these different sources consist, in the one case, of 
some fragments of a few skeletons of former races, which, by some 
fortuitous circumstances, have to this day resisted the disintegrating 
forces of nature ; and, in the other, of a number of specimens of 
man’s handicraft works, which, being largely made of such en- 
durable substance as flint, are more abundantly met with. The 
successive modifications which these respective materials have 
undergone during a long series of ages, though different in kind, 
are found to bear a decided ratio to the progress of human intelli- 
gence. Thus, taking the human skull at the starting-point of 
humanity as comparable to that of one of the higher apes, we 
know, as a matter of fact, that during the onward march of time 
it has undergone some striking changes, both in form and capacity, 
before reaching the normal type of modern civilised races — changes 
which can be largely classified in chronological sequence (see pp. 
99-108). Similarly, the artificial products of man’s hands show 
a steady improvement in type, technique, and efficiency, commen- 
surate with his progressive knowledge of the laws of nature and his 
ability in applying them to mechanical and utilitarian purposes. 
Indeed, the trail of humanity along its entire course is strewn with 
the discarded weapons and tools which, from time to time, had to 
give way to others of greater efficiency. Such obsolete objects are 
now only collected as curiosities to be preserved in archaeological 
museums (see pp. 109-117). 
The main object of these preliminary remarks is to emphasise 
the nature and true significance of the methods by which anthro- 
pologists have been enabled to prosecute their researches far 
