288 SCIENCE PROGRESS 



and the greater development of the tongue-muscles therein 

 implied, have been developed independently in more than one 

 branch of the evolving Primates ? The phenomenon of con- 

 vergence, or parallelism in evolution, is one that has long been 

 familiar to naturalists. There is the famous case of the 

 cephalopod eye, which simulates so closely in its structure the 

 eye of a vertebrate. In two widely separated branches of the 

 animal kingdom the same need was met in the same way. 

 Again, there is in Australia a little animal called the pouched 

 mole. This creature is a marsupial and is consequently allied 

 to the kangaroos. But it lives underground, and in its appear- 

 ance, and in the adaptation of its limbs and form to a 

 subterranean mode of life, the little beast exactly resembles the 

 real moles of Europe. In this case, too, the same need has been 

 met in the same way. With our present knowledge of the 

 early Hominidse it is of course impossible to speak with con- 

 fidence of the factors at work in the evolution of those creatures, 

 but it is quite likely that this principle of convergence played 

 some part in that process. Our second hypothesis, indeed, 

 necessitated it in certain minor respects. But when we recall 

 in imagination the conditions under which the divers sorts of 

 half-men lived, we can see that convergence may have been a 

 most conspicuous phenomenon in their progress. They were 

 highly gregarious animals, whose very survival must constantly 

 have depended upon the power of the individuals efficiently to 

 combine. And to combine effectively it was before all things 

 necessary that they should be able to communicate with one 

 another. The power of speech was a crying need of the 

 advancing Primates — a want no less urgent than muscular 

 fossorial limbs to the marsupial of mole-like habits. It was 

 language that transformed the horde into the tribe. The 

 creatures were probably widely dispersed over the earth 

 whilst they were yet speechless. And rudimentary powers of 

 speech may thus have been acquired independently by more 

 than one species ; and this, not blood-relationship, may be the 

 explanation of the man-like symphysis of the Heidelberg jaw. 

 And those who are impressed with the neandertaloid features of 

 that specimen might go farther and re-establish the connection 

 between heidelbergensis and neandertalensis. The descent would 

 then work out as shown in fig. 5. 



On this last hypothesis the common ancestor, " X," is con- 



