EVOLUTION MADE PLAIN 19 
As man belongs in the same group with them 
the chasm is not so great in the sum of phys¬ 
ical characters as is that between the fish and 
the reptile groups, or between the reptiles and 
the mammals. In regard to man and the higher 
apes the dividing line, viewed from the stand¬ 
point of descent, is vertical rather than hori¬ 
zontal—like that between mammals and birds. 
There are no species, extinct or extant, be¬ 
tween man and the ape. It is not necessary 
for the proof of evolution that there should be. 
“Missing links” are not more required here 
than they are between birds and mammals 
which were evolved side by side from reptiles. 
If ten feet below the topmost bough of a tree 
there is another branch it is not necessary to 
show that there are, or have been, intermediate 
branches to prove that both grew from the same 
trunk. Missing links are required only in the 
line of descent. 
Discoveries of the fossil remains of man are 
rare for many reasons. (1) Land animals 
rarely leave their remains in the sediment of 
sea and lake. (2) There is small chance of 
the sediment containing the fossils of recently 
arrived animals—more especially of man, the 
latest arrival—being lifted above the water 
level because of the slow movements of the 
earth's crust. (3) Only those animal remains 
that are buried in localities where they will 
be impregnated with certain mineral salts will 
be preserved. (4) They must be able to resist 
those destructive agencies (especially erosion 
by water) that disintegrate the rock in which 
they are embedded if they are to come down 
to us as evidence. (5) Only a small part of 
