December 19, 1895] 



NATURE 



51 



In a recent communication (Nature, vol. li. p. 533) on the 

 ;ige of the earth, I gave 2CXX) feet as the maximum thickness 

 of the Pliocene system, and this is the thickness which it 

 attains in Europe (Sicily) ; but in India this is far surpassed, the 

 Siwalik Hills, which are 14,000 or 15,000 feet in height, present 

 for examination at least 10,000 feet of Pliocene deposits. 



In Europe the Miocene does not exceed 6000 feet in thickness ; 

 but it may be regarded as quite certain that the duration of 

 Miocene time was much greater than that of the Pliocene, and 

 since in Europe the thickness of these two systems is as 3 : i, 

 we shall probably arrive at a just result if we take three times 

 the thickness of the Pliocene of India to represent, on our scale, 

 the duration of the Miocene period. We thus obtain for the 

 proportional duration of our three periods the relation 0*4 : I : 3, 

 which to the geologist has a veridical look. 



In order to employ this scale to indicate the rate at which 

 evolution in any particular case has proceeded, we must be able 

 to give a numerical expression to the evolutional change also ; 

 and this can be accomplished, 

 at least partially, in the case of 

 the human race. For with it, 

 the organ of organs is not so 

 much the hand as the brain, 

 :ind of this the volume at least 

 ;an be ascertained, whenever 

 we can possess ourselves of a 

 human skull. In the following 

 diagram the scale of time is 

 plotted on the ordinate o T to 

 the right, and the cranial 

 capacity on the abscissa o c. 

 The Neanderthal race is as- 

 signeil to the middle of the 

 I'leistocene, on the evidence 

 of the Spy remains ; the Java 

 fossil is placed at the beginning 

 of that period. Dr. IJubois 

 is in possession of evidence 



which, when fully worked out, 



will fix its geological position 



with greater precision than we 



can attain at present; but so 



fer as his published statements 



go, they point to that which 



we have assigned as the most 



probable horizon. The anthro- 

 poid apes are shown on the 



left of the diagram 5 the chim- 

 panzee and gorilla are sup- 

 posed to be the descendants of 



a chain of ancestors, which 



converge towards a common 



stem, on or near which Dryo- 



pithecus of the Middle Miocene 



IS situated. This, which we 



may call the Dryopithccus 



stem, converges towards Ilylo- 



bates. It will be observed that 



•we have drawn all these lines 



■of descent sloping towards 



the left, as they must almost 



certainly have done if there be 



any truth in evolution, and consequently the further back we go 



to find the origin of the human stem, the more brutal we make 



the primitive ancestor. 



If now we draw a line through the point occupied by the 



are known to possess fossils, and of those specimens which have 

 been obtained from the series specially distinguished as fossil- 

 iferous, the proper geological position is not known. The 

 Siwalik beds, if carefully searched, might be expected, from 

 what we already know, to yield results no less precious to science 

 than those obtained by Marsh and Cope in the famous deposits 

 of the Green River Basin. It might be well worth considering 

 whether an expedition could not be despatched from Europe for 

 the special study of the Siwalik sediments. 



The suggestion offered by the curve running through the apes 

 to man is that he is of comparatively recent origin, and deriva- 

 tive from the stem of the gorilla or chimpanzee before these 

 species had acquired their existing specialised characters. The 

 straightness of the curve has an aspect almost miraculous, not a 

 discommendation to the minds of some ; but it has this positive 

 advantage, that by linking on the human to the pithecoid stem 

 at a high level, it saves us from the invention of a superfluity ot 

 imaginary predecessors, and all that tends to parsimony in this 



PLEISTOCENE 



we find that it passes very close to the Neanderthal, and this 

 suggests that the evolution of the human race has proceeded at 

 a very uniform rate throughout the whole of Pleistocene time, 

 while the excessive slope of the curve suggests that this rate was 

 a very rapid one. If further we produce this line to the left, it 

 will be found to intersect the ancestral stems of the highest 

 anthropoid apes in the middle of the Pliocene period, and it is 

 to this period that Anthropithecus sivalensis of Lydekker, a 

 chimpanzee having affinities with man and Hylobates, has been 

 assigned. The exact horizon from which the palate, on which 

 this species is founded, was obtained is not known ; and in this 

 connection one is constrained to express the great regret that all 

 biologists must feel at the imperfect manner in which the Siwalik 

 strata have been investigated. Beds said to be unfossiliferous 



NO. 1364, VOL. 53] 



Cubic Centimetres. 



direction is an evident gain. The evolution along a line of 

 descent is not confined to the acquisition of new characters, but 

 includes the loss of others ; and thus I can see no reason why the 

 human ancestry should not have proceeded from the compara- 



average European skull, and that occupied by the javan skull, tively highly organised ancestors of the gorilla or chimpanzee. 



rather than from the more primitive predecessors of Hylobates. 

 To those who think otherwise the curve shown by dotted lines 

 will appear the more plausible ; if the Neanderthal skull be lifted 

 a little upwards in the scale of time, a curve can be made to 

 pass through it, the European and Javan skulls, and this when 

 prolonged downwards will approximate to the stem either of 

 Pliopithecus (a Miocene gibbon) or the more brutal Dryo- 

 pithccus. This would be a curve indicating greatly accelerated 

 development as it approaches modern times ; a contingency 

 which a preliminary examination of other groups shows to be by 

 no means impossible. Other curves no doubt could be drawn 

 according to fancy of the individual ; the true curve may 

 possibly reward some fortunate investigator of the Siwalik Hills. 



W. J. SOLLAS. 



