134 “The Descent of Man” 
indicate a common descent, and cannot be explained as phenomena 
of convergence. 
I believe I have shown in the above sketch that a theory which 
derives man directly from lower forms without regarding apes as 
transition-types leads ad absurdum. The close structural relation- 
ship between man and monkeys can only be understood if both are 
brought into the same line of evolution. To trace man’s line of 
descent directly back to the old Eocene mammals, alongside of, but 
with no relation to these very similar forms, is to abandon the method 
of exact comparison, which, as Darwin rightly recognised, alone 
justifies us in drawing up genealogical trees on the basis of resem- 
blances and differences. The farther down we go the more does the 
ground slip from beneath our feet. Even the Lemuridae show very 
numerous divergent conditions, much more so the Eocene mammals 
(Creodonta, Condylarthra), the chief resemblance of which to man 
consists in the possession of pentadactylous hands and feet! Thus 
the farther course of the line of descent disappears in the darkness 
of the ancestry of the mammals. With just as much reason we might 
pass by the Vertebrates altogether, and go back to the lower Inverte- 
brates, but in that case it would be much easier to say that man 
has arisen independently, and has evolved, without relation to any 
animals, from the lowest primitive form to his present isolated and 
dominant position. But this would be to deny all value to classifica- 
tion, which must after all be the ultimate basis of a genealogical tree. 
We can, as Darwin rightly observed, only infer the line of descent 
from the degree of resemblance between single forms. If we 
regard man as directly derived from primitive forms very far back, 
we have no way of explaining the many points of agreement between 
him and the monkeys in general, and the anthropoid apes in par- 
ticular. These must remain an inexplicable marvel. 
I have thus, I trust, shown that the first class of special theories 
of descent, which assumes that man has developed, parallel with the 
monkeys, but without relation to them, from very low primitive forms 
cannot be upheld, because it fails to take into account the close 
structural affinity of man and monkeys. I cannot but regard this hypo- 
thesis as lamentably retrograde, for it makes impossible any application 
of the facts that have been discovered in the course of the anatomical 
and embryological study of man and monkeys, and indeed prejudges 
investigations of that class as pointless. The whole method is per- 
verted; an unjustifiable theory of descent is first formulated with the 
aid of the imagination, and then we are asked to declare that all 
structural relations between man and monkeys, and between the 
different groups of the latter, are valueless,—the fact being that they 
are the only true basis on which a genealogical tree can be constructed. 
