178 MR. R. I. POCOCK ON A HAINAN GIBBON, [May 16, 
This conclusion respecting the descent of the Gibbons may be 
inferred from their habits alone, quite apart from structure. 
If the Anthropoid Apes be ranged in series according to 
proficiency in bipedal locomotion, the order will be (1) Gibbons, 
(2) Gorillas, (3) Chimpanzees, (4) Orangs. Gibbons not only stand 
erect and habitually walk without putting the hands to the 
ground; they can even run with astonishing speed, a speed indeed 
comparable to that of Man, allowance being made for difference in 
size. Like Man they race away when scared; and, unlike the 
other Anthropoid Apes, they do not use their arms as crutches. 
Sometimes also, but rarely, they leap over the ground with both 
feet together *. 
Gorillas can stand and walk upright, but not with the ease 
of Gibbons, and it may be doubted if they ever run erect or leap, 
i.e. progress with both feet off the ground at one time; and 
they probably never run from danger, standing upright, as Man 
and Gibbons do. Their usual walk is quadrupedal. 
Chimpanzees, too, are essentially quadrupedal; and under 
ordinary conditions, and when in perfect health, almost always get 
over the ground on “all fours,” like a Baboon or Rhesus. In this 
respect, indeed, they more resemble the Cercopithecoid Monkeys 
than does any other Anthropoid Ape; and they are able to cover 
the ground with much greater speed than either Gorillas or Orang- 
Utans ; but I am unable to say if their quadrupedal method is so 
fast as the bipedal method of Gibbons. Like Baboons, they can 
stand erect and walk to a certain extent, but not with the facility 
of Gorillas. 
The gait of young Orang-Utans may be described as a clumsy 
quadrupedal shuffle, J never saw one stand unsupported by the 
arms. Weakness of leg and weight of body make exclusively 
bipedal action, if not an impossibility, at least so great an effort 
that it may be doubted if it is ever resorted to. Their whole 
organisation suggests unfitness for terrestrial locomotion. 
Thus, if the Apes be classified according to their quadrupedal 
activity on the ground, they will stand:—(1) Chimpanzees, 
(2) Gorillas, (3) Orangs, (4) Gibbons. 
It is interesting to compare this series with one based upon 
dexterity in climbing and addiction to arboreal life. It is: 
(1) Gibbons, (2) Orangs, (3) Chimpanzees, (4) Gorillas. The 
Gibbons stand quite alone both in method and expertness; the 
others differ inter se merely in degree. 
The foregoing results may be briefly summarised as follows :— 
The Gibbons are the most expert climbers and bipedal walkers, 
the least expert quadrupedal walkers. The Orangs rank second 
in climbing, third in quadrupedal and fourth and last in bipedal 
activity. The Gorillas take fourth place in climbing, second in 
bipedal and second in quadrupedal activity. The Chimpanzees 
* These and the following statements and reflections are based upon my own 
observations of the Anthropoid Apes that have come under my notice in the Society’s 
Gardens. 
