66 CHAPTER 3 | Living Primatesorder— especially the apes—are more differences of degree
than differences of kind.Living Primates
Except for a few species of Old World monkeys who live
in temperate climates and humans who inhabit the entire
globe, living primates inhabit warm areas of the world. We
will briefly explore the diversity of the five natural group-
ings of living primates: lemurs and lorises, tarsiers, New
World monkeys, Old World monkeys, and apes. We will
examine each group’s distinctive habitat, biological fea-
tures, and behavior.Lemurs and Lorises
Although the natural habitat of lemurs is restricted to the
large island of Madagascar (off the east coast of Africa),
lorises range from Africa to southern and eastern Asia.
Only on Madagascar, where there was no competition
from anthropoid primates until humans arrived, are le-
murs diurnal, or active during the day; lorises, by contrast,
are all nocturnal and arboreal.
All these animals are small, with none larger than a
good-sized dog. In general body outline, they resemblecombination of pad and nail provides the animal with an
excellent prehensile (grasping) device for use when mov-
ing from branch to branch. The structural characteristics
of the primate foot and hand make grasping possible; the
digits are extremely flexible, the big toe is fully opposable
to the other digits in all but humans and their immediate
ancestors, and the thumb is opposable to the other digits
to varying degrees.
The retention of the flexible vertebrate limb pattern in
primates was a valuable asset to evolving humans. It was,
in part, having hands capable of grasping that enabled our
own ancestors to manufacture and use tools and to em-
bark on the evolutionary pathway that led to the revolu-
tionary ability to adapt through culture.
To sum up, what becomes apparent when humans
are compared to other primates is how many of the char-
acteristics we consider distinctly human are not in fact
uniquely ours; rather, they are variants of typical primate
traits. We humans look the way we do because we are pri-
mates, and the differences between us and others of thisprehensile Having the ability to grasp.
opposable Able to bring the thumb or big toe in contact with
the tips of the other digits on the same hand or foot in order to
grasp objects.Wherever there is competition from the anthropoid primates, prosimian species, such as this
loris on the right, retain the arboreal nocturnal patterns of the earliest fossil primates. Notice its
large eyes, long snout, and moist split nose—all useful in its relatively solitary search for food
in the trees at night. In contrast, only on the large island of Madagascar off the eastern coast
of Africa, where no anthropoids existed until humans arrived, have prosimians come to occupy
the diurnal ground-dwelling niche as do these ring-tailed lemurs. While all prosimians still rely
on scent, marking their territory and communicating through smelly messages, daytime activity
allowed the prosimians on Madagascar to become far less solitary. Also notice the difference in
the size of the eyes in these two groups. Just as it would be incorrect to think of prosimians as
“less evolved” than anthropoid primates because they bear a closer resemblance to the ances-
tral primate condition, it is also incorrect to think of lorises as less evolved compared to lemurs.Visual Counterpoint© blickwinkel/Alamy © Kevin Schafer/Peter Arnold, Inc.