By ALFRED R. WALLACE.
If the skeleton of an orang-outang and a chimpanzee be compared with
that of a man, there will be found to be the most wonderful resemblance,
together with a very marked diversity. Bone for bone, throughout the
whole structure, will be found to agree in general form, position, and
function, the only absolute differences being that the orang has nine
wrist bones, whereas man and the chimpanzee have but eight; and the
chimpanzee has thirteen pairs of ribs, whereas the orang, like man, has
but twelve. With these two exceptions, the differences are those of
shape, proportion, and direction only, though the resulting differences
in the external form and motions are very considerable. The greatest of
these are, that the feet of the anthropoid or man-like apes, as well as
those of all monkeys, are formed like hands, with large opposable thumbs
fitted to grasp the branches of trees, but unsuitable for erect walking,
while the hands have weak, small thumbs, but very long and powerful
fingers, forming a hook, rather than a hand, adapted for climbing up
trees and suspending the whole weight from horizontal branches. The
almost complete identity of the skeleton, however, and the close
similarity of the muscles and of all the internal organs, have produced
that striking and ludicrous resemblance to man, which every one
recognizes in these higher apes, and, in a less degree, in the whole
monkey tribe; the face and features, the motions, attitudes, and
gestures being often a strange caricature of humanity. Let us, then,
examine a little more closely in what the resemblance consists, and how
far, and to what extent, these animals really differ from us.
Besides the face, which is often wonderfully human--although the absence
of any protuberant nose gives it often a curiously infantile aspect,
monkeys, and especially apes, resemble us most closely in the hand and
arm. The hand has well-formed fingers, with nails, and the skin of the
palm is lined and furrowed like our own. The thumb is, however, smaller
and weaker than ours, and is not so much used in taking hold of
anything. The monkey's hand is, therefore, not so well adapted as that
of man for a variety of purposes, and cannot be applied with such
precision in holding small objects, while it is unsuitable for
performing delicate operations, such as tying a knot or writing with a
pen. A monkey does not take hold of a nut with its forefinger and thumb,
as we do, but grasps it between the fingers and the palm in a clumsy
way, just as a baby does before it has acquired the proper use of
its hand. Two groups of monkeys--one in Africa and one in South
America--have no thumbs on their hands, and yet they do not seem to be
in any respect inferior to other kinds which possess it. In most of the
American monkeys the thumb bends in the same direction as the fingers,
and in none is it so perfectly opposed to the fingers as our thumbs are;
and all these circumstances show that the hand of the monkey is, both
structurally and functionally, a very different and very inferior organ
to that of man, since it is not applied to similar purposes, nor is it
capable of being so applied.
When we look at the feet of monkeys we find a still greater difference,
for these have much larger and more opposable thumbs, and are therefore
more like our hands; and this is the case with all monkeys, so that even
those which have no thumbs on their hands, or have them small and weak
and parallel to the fingers, have always large and well-formed thumbs on
their feet. It was on account of this peculiarity that the great French
naturalist Cuvier named the whole group of monkeys Quadrumana, or
four-handed animals, because, besides the two hands on their fore-limbs,
they have also two hands in place of feet on their hind-limbs. Modern
naturalists have given up the use of this term, because they say that
the hind extremities of all monkeys are really feet, only these feet
are shaped like hands; but this is a point of anatomy, or rather of
nomenclature, which we need not here discuss.
Let us, however, before going further, inquire into the purpose and
use of this peculiarity, and we shall then see that it is simply an
adaptation to the mode of life of the animals which possess it. Monkeys,
as a rule, live in trees, and are especially abundant in the great
tropical forests. They feed chiefly upon fruits, and occasionally eat
insects and birds'-eggs, as well as young birds, all of which they find
in the trees; and, as they have no occasion to come down to the ground,
they travel from tree to tree by jumping or swinging, and thus pass the
greater part of their lives entirely among the leafy branches of lofty
trees. For such a mode of existence, they require to be able to move
with perfect ease upon large or small branches, and to climb up rapidly
from one bough to another. As they use their hands for gathering fruit
and catching insects or birds, they require some means of holding on
with their feet, otherwise they would be liable to continual falls, and
they are able to do this by means of their long finger-like toes and
large opposable thumbs, which grasp a branch almost as securely as a
bird grasps its perch. The true hands, on the contrary, are used chiefly
to climb with, and to swing the whole weight of the body from one branch
or one tree to another, and for this purpose the fingers are very long
and strong, and in many species they are further strengthened by being
partially joined together, as if the skin of our fingers grew together
as far as the knuckles. This shows that the separate action of the
fingers, which is so important to us, is little required by monkeys,
whose hand is really an organ for climbing and seizing food, while their
foot is required to support them firmly in any position on the branches
of trees, and for this purpose it has become modified into a large and
powerful grasping hand.
Another striking difference between monkeys and men is that the former
never walk with ease in an erect posture, but always use their arms in
climbing or in walking on all-fours like most quadrupeds. The monkeys
that we see in the streets dressed up and walking erect, only do so
after much drilling and teaching, just as dogs may be taught to walk in
the same way; and the posture is almost as unnatural to the one animal
as it is to the other. The largest and most man-like of the apes--the
gorilla, chimpanzee, and orang-outang--also walk usually on all-fours;
but in these the arms are so long and the legs so short that the body
appears half erect when walking; and they have the habit of resting on
the knuckles of the hands, not on the palms like the smaller monkeys,
whose arms and legs are more nearly of an equal length, which tends
still further to give them a semi-erect position. Still they are never
known to walk of their own accord on their hind legs only, though they
can do so for short distances, and the story of their using a stick and
walking erect by its help in the wild state is not true. Monkeys, then,
are both four-handed and four-footed beasts; they possess four hands
formed very much like our hands, and capable of picking up or holding
any small object in the same manner; but they are also four-footed,
because they use all four limbs for the purpose of walking, running, or
climbing; and, being adapted to this double purpose, the hands want the
delicacy of touch and the freedom as well as the precision of movement
which ours possess. Man alone is so constructed that he walks erect with
perfect ease, and has his hands free for any use to which he wishes
to apply them; and this is the great and essential bodily distinction
between monkeys and men.
We will now give some account of the different kinds of monkeys and the
countries they inhabit.