1894- CORRESPONDENCE. 399 



Natural Selection has been the cause of his development. The matter is not 

 mended by showing that the erect position is better than the crawling, because it is 

 necessary for Natural Selection, not only to show that the final result is better than 

 the initial, but that every step on the road carried an advantage with it. The 

 problem is certainly difficult, but I do not think it is insuperable, and I have a 

 suggestion to offer which may, perhaps, lead to a partial explanation. 



The idea was suggested to me by watching mungooses in India ; when these 

 animals wish to look around them, they sit up like a dog begging, bringing the head 

 as high as possible. Now, if we suppose that in the commencement of the Glacial 

 Epoch, the anthropoid was liable to attack, either from carnivora, as famished 

 wolves, or from his own species, evidently extreme circumspection would be 

 requisite ; a single moment of inattention might prove fatal. Evidently, the result 

 would be that those individuals who were able to carry the head aloft persistently 

 would have an advantage over those who could only raise it up now and then. 



This may account for the head being carried high, and the back being straight, 

 but by itself it will not account for the disuse of the fore-limbs in locomotion ; 

 it would be more likely to lead to excessive lengthening of the arms, so that while 

 the back was straight, the hands could be rested on the ground. 



I have postulated that this anthropoid had sufficient intelligence to use stones 

 as weapons ; now, stooping to pick up a stone would necessitate being off guard for 

 a moment, during which a sudden attack might be made ; moreover, if the ground 

 was frozen hard, detaching a stone would take time, and necessitate a prolonged 

 period of helplessness, during which an attack would be disastrous ; evidently it. 

 would be desirable for the animal to carry a suitable stone with it, by throwing: 

 which the adversary might be, if not killed, momentarily disabled, and time gained 

 to pick up another stone. It would be difficult or nearly impossible to use the arm 

 belonging to the hand carrying the stone in locomotion, besides which it might be- 

 desirable to have it free in case of sudden attack. So the normal progression would 

 probably be nearly erect on the hind limbs, with occasional assistance from the arm 

 not used in carrying the stone. 



In fighting, or in hurling missiles, extreme firmness on the legs would be 

 desirable; the slightest stumble might prove fatal. Now, those individuals who 

 dispensed with the assistance of the arm as much as possible, and used the legs only, 

 would come to have stronger legs and be steadier on them than those who made 

 much use of the arm in locomotion ; they would consequently have an advantage in 

 the struggle for existence. 



If we admit the possible transmission of acquired characters, this steadiness on 

 the legs might be transmitted ; but it is not necessary to assume this. My argument 

 is that those individuals who had a congenital dislike for using the arm in 

 locomotion, or preference for the unaided use of the legs, would become steadier, 

 and so have an advantage over their fellows ; and it is this partiality for using the 

 legs only which I suppose to be transmitted. 



The erect posture, and the habit of using only the legs in locomotion, being 

 acquired, there would no longer be any advantage in having the arms long enough 

 to touch the ground. Now, in hurling missiles, too long an arm would be a decided 

 disadvantage, as it would make the animal liable to over-balance himself. Too 

 short an arm would be a disadvantage, obviously, too. The arm would, therefore, 

 shorten to some extent, until the best length for throwing stones had been attained. 

 The advantages of a firm grasp, either in throwing or in using weapons, would also 

 lead to modifications in the form of the hand. 



I have laid considerable stress on the advantage of carrying a stone, so as to be 

 at once ready for attack. Remembering that this missile must have frequently- 

 failed to hit its mark, it may be supposed that I have laid too much stress on a very 

 slight advantage. But I suppose the struggle for existence to be terribly severe. 

 Food was scarce, and therefore the anthropoid had to venture far afield to seek it, 

 or starve. Trees were scarce, so he could not seek safety in climbing. Probably 

 the change from a frugivorous to an omnivorous diet was contemporaneous. After 

 having killed his assailant, he must often have been too terrified and exhausted to^ 



