No primate exhibits all these features, and indeed the diversity of primate forms has produced disagreement as to
their proper classification.
The smallest primates are weighed in tens of grams, while the Gorilla
typically weighs 140 to 180
kilograms (300 to 400 pounds).
Nonhuman primates are found throughout the tropical areas of India, Africa, Asia, and South America. A few species
also live in temperate latitudes, but lack of winter food supply limits their adaptability to these climates.
Most primates have binocular vision and forward-facing eyes, two characteristics that are necessary for
Although their vision is highly developed, primates have shortened muzzles and a correspondingly reduced sense of
Except for two species, all primates have five digits on each hand and foot. All have prehensile (grasping
hands, and all except man have prehensile feet.
Although the opposable (freely moving) thumb is present in most primates, it is particularly developed in man, making
him capable of delicate manipulation.
A trend in primate evolution has been toward a more elaborate brain. In higher primates, the neocortex
functions to receive, analyze, and synthesize information from the senses.
The brain of anthropoids is larger, relative to body weight, than that of prosimians and is characterized by a
complicated pattern of folds and fissures on the surface.
Another evolutionary trend in primates involves the development of offspring
both before and after birth.
Gestation periods (The period of development in the uterus from conception until birth) are relatively long, allowing
for the development of the more complex brain.
Ever since recorded history began, and probably before, people have found pieces of rock and other hard
material with indentations from the remains of dead organisms. These are called fossils, and the totality of
these artifacts and their placement in rock striations is referred to as the fossil
The fossil record is one of the primary sources of data relevant to the study of evolution. Scientists examine fossils in
order to understand the process of evolution and the way specific species have evolved.
methods, such as radiometric (but not carbon-14
, which works only for 0-50,000 years before
present), show that some of these fossils are tens of millions of years old.
Various dating methods have been used and are used today, and while there is some variance in the results from
these methods, nearly all of them provide evidence for a very old Earth and for evolution.
The geologist sees Relative Time where two or more events are compared
without any numerical