1886. ]} The Making of Man. 497 
gained except by a species which dwelt wholly on the ground. 
And life in trees absolutely requires the use of the arms as loco- 
motive organs, and prohibits that freeing of them from this duty 
which exists in man. When man ascends trees he is obliged to 
return to the habit of his ancestors and use his arms as organs of 
progression. It seems evident, therefore, that if man descended 
: from the apes his ancestral species must have been a form which 
had fully given up its life in trees, and had become almost as 
| awkward in climbing as man now is, ere it fairly began to change 
4 from ape into man. 
i 
The adoption of a surface residence by any ape would necessi- 
tate certain changes in structure. Tree-dwelling apes, when they 
descend to the ground, present us frequently with an awkward 
compromise between the horizontal and the vertical modes of 
motion. Neither of these modes is natural to them, and to be- 
come properly adapted to either some change of structure is 
necessary, Many of them progress in the true quadrupedal man- 
ner, and in one ground-living tribe, the baboons, the structure of 
the body has suffered an accordant change. They have become 
true quadrupeds. 
In other cases there is an inclination towards an erect mode of 
- motion. Even among the lemurs this is occasionally displayed. 
Some species of these progress on the ground by jumps, the body 
being semi-erect and the arms held above the head. The anthro- 
poid apes all have a curious mode of progression on the ground, 
intermediate between the erect and the horizontal methods. The 
orang, the chimpanzee and the gorilla alike use their four limbs in 
Progression, but in a manner very unlike that of ordinary quad- 
 Tupeds. They swing the body in a curious fashion between the 
arms. It is a sort of half-jumping, half-walking motion. Rest- 
ing the body on the hands, the animal swings itself between the ~ 
arms, and moves forward by a quick succession of such lifts and — 
angs. In this movement the orang and the chimpanzee bring 
their closed knuckles to the ground, but the gorilla is said to 
“ep the hand open and apply the palm to the ground. The — 
Outer edge rather than the sole of the foot touches the ground. 
: ie _ *he whole movement is as awkward as is that of man when he- 
os . = 3 pts to climb trees, and seems to indicate that there can be- 
e ma Satisfactory compromise between the two life-habits. A sur- : 
o eae animal must. tend to become either a quadruped or o 
ppi. 
ERENLER S a ee 
ee =n aces, a , 
