Data for the Problem of Evolution in Man. 



131 



Now these tables indicate very important conclusions : — 



(i) The hand is a very highly correlated organ, far more highly 

 correlated than the skull and even somewhat more so than the long 

 hones.* We are accustomed to give man precedence in life on 

 account of his brain power, and it might, perhaps, be thought that 

 the brain case would be highly correlated in its parts. Yet what we 

 find is that the skull is extremely individual, its correlations are low 

 and a man could be readily identified by head measurements, whereas 

 hand measurements would be immensely less safe. In other words 

 the hand so far as its dimensions go (we put aside markings) is far 

 closer to a type than the skull. 



(ii) The parts of the left hand are distinctly more closely corre- 

 lated than those of the right. The only exception is the correlation 

 of R ii and R iv, which is greater than that of L ii and L iv, but the 

 difference here is considerably less than the probable error of the differ- 

 ence, and the general rule appears to be quite certain. Now this is a 

 most remarkable- result, but again how is it to be interpreted 1 Is it a 

 result of selection or a use effect 1 For the same organ it is a rule 

 that the greater the selection the less the variability and the less the 

 correlation. Exceptions there can be, which will be discussed else- 

 where, but this appears the general rule. Is the less variability and 

 correlation of the right hand a result of greater selection, or is it after 

 all a result of use 1 If the latter we see how hopeless it is to associate 

 constancy of correlation, or even of regression coefficients with the idea 

 of local races. Indeed the further we enter into the quantitative side 

 of the problem of evolution the more important appears the de- 

 termination of the influence of growth and use on both variability and 

 correlation. Why is the right hand less variable and less highly 

 correlated than the left 1 Is the answer the same as to the question : 

 Why is civilised man less variable and less highly correlated than 

 civilised woman 1 



(iii) The order of correlation of the first finger joints is identical for 

 both hands. This order is as follows : — 



(a) The external fingers have the least correlation and the little 



finger always less than the index. 



(b) A finger has always more correlation with a second than with 



any other finger from which it is separated by the second. 



Table IV(c) exhibits the correlation of corresponding members on 

 both sides. It will be observed that again the extreme pairs show 



* Compare the table on p. 181 of the memoir " On the Beconstruction of the 

 Stature of Prehistoric Races" ('Phil. Trans.,' A, vol. 192). The index and 

 middle finger first joints are more highly correlated than femur and tibia ; the 

 middle and ring finger first joints than humerus and radius, the index and ring- 

 finger first joints than femur and humerus. 



L 2 



