96 Darwin, and after Darwin. 



On the other hand, however, there is reason to doubt 

 whether this form of tibia in man is really a survival 

 from his quadrumanous ancestry. For, as Boyd- 

 Dawkins and Hartmann have pointed out, the degree 

 of flattening presented by some of these ancient 

 human bones is greater than that which occurs in any 

 existing species of anthropoid ape. Of course the 

 possibility remains that the unknown species of ape 

 from which man descended may have had its tibia 

 more flattened than is now observable in any of the 

 existing species. Nevertheless, as some doubt attaches 

 to this particular case. I do not press it and, indeed, 

 only mention it at all in order that the doubt may be 

 expressed. 



Similarly, I will conclude by remarking that several 

 other instances of the survival of vestigial structures 

 in man have been alleged, which are of a still more 

 doubtful character. Of such, for example, are the 

 supposed absence of the genial tubercle in the case 

 of a very ancient jaw-bone of man, and the disposition 

 of valves in human veins. From the former it was 

 argued that the possessor of this very ancient jaw-bone 

 was probably speechless, inasmuch as the tubercle in 

 existing man gives attachment to muscles of the 

 tongue. From the latter it has been argued that all 

 the valves in the veins of the human body have 

 reference, in their disposition, to the incidence of blood- 

 pressure when the attitude of the body is horizontal, 

 or quadrupedal. Now, the former case has already 

 broken down, and I find that the latter does not hold. 

 But we can well afford to lose such doubtful and 

 spurious cases, in view of all the foregoing unquestion- 

 able and genuine cases of vestigial structures which are 



