266 SCIENCE PROGRESS 



There are other advances in prehistory which might be 

 discussed at almost any length : the minute characteristics of 

 the different types of Paleolithic implements — Prof. Sollas's 

 description of the implements of the Aurignacian Age is 

 especially exhaustive — the exact division of the Paleolithic into 

 subordinate ages, and the vexed question of the correlation of 

 those subordinate ages with the glacial and interglacial epochs : 

 but more interesting still is the light thrown on the nature of 

 the early men themselves. What has palaeontology to say 

 about the descent of man ? This question is even more 

 pertinent to-day than it was fifteen years ago, for the progress 

 of biology has of course thrown much doubt upon the whole 

 hypothesis of gradual evolution as advocated by Darwin. 

 There are now some reasons for thinking that evolution takes 

 place by saltation, or " mutation," not by the imperceptible 

 merging of one species into another species. Palaeontology 

 ought to have much to say in this debate, and it is strange 

 to find that Lord Avebury, writing as recently as 1912, should 

 discuss the supposed linking-up of species without so much as 

 a reference to Mendel, to De Vries, or to Bateson. Even Sollas, 

 thinking no doubt that the subject would lead him too far 

 from his main thesis, does no more than hint that the problem 

 exists. 



It has often been said that the weakest side of the case for 

 organic evolution is in geology. I do not think that there has 

 ever been very much force in that criticism ; on the contrary, 

 geological discovery has probably given evolution more support 

 than the earlier evolutionists would have dared to hope. But 

 when the criticism is directed not against organic evolution in 

 general, but against the particular hypothesis of gradual 

 evolution, it certainly has point. There are cases in which 

 fossil species do appear to merge, but the phenomenon is not to 

 be seen on the great scale that one would have expected if the 

 Darwinian hypothesis were true. The cases of apparent merging 

 present a difficulty to the Mendelians, but the latter are able to 

 explain the instances of variable species among living animals, 

 and it must be remembered that mutations are not necessarily 

 large " sports." Of course many of the gaps between species 

 are too large to have been filled by a single mutation, but 

 in general the constancy of species in time and the very wide- 

 spread phenomenon of gaps are more readily explicable on the 



