The Evolution of Primates

The earliest primates began to appear after the time that dinosaurs had become extinct beginning almost 50 to 60 millions years ago. They differed from other mammals in a number of ways, all of which can be traced directly to the biological makeup of modern human.

They tended to be larger and they had larger brain on proportion to their body size.

Perhaps the most important feature of the early primates is that they were arboreal; that is, while they exploited food sources on the ground as well as those in trees, for the most part they lived in the trees.

Because they lived in trees, early primates were subject to selective pressures that brought about a number of other changes. Moving through the trees required improved eyesight and motor coordination.

This led not only to the evolution of stereoscope sight with greater depth perception, which was needed for jumping from one branch to another, but also to color vision, which is useful in telling live branches from dead ones or ripe from unripe fruit.

Other senses changed along with eyesight. The sense of touch became more important, since the precision required for moving in the trees had life-or-dead meaning for primates. An animal that is running along on the ground can make a mistake in judgment, fall, get up, and be on its way again, but a slight mistake in the treetops can be fatal.

The forelimbs, or hands of primates therefore became more sensitive, and the fingers became more mobile. Claws were replaced by flat nails and most important the thumb and big toe became opposable, which means that they could be moved opposite to some or all of the fingers or toes.

This means that primates could manipulate objects with their hands, rather than grasping them with their teeth, as other mammals do. Later on, the arms, grew distinct from the legs and became able to rotate, flex, and extend.

All of these changes are important in terms of the way early primates gathered food and caught small animals both in trees and on the ground.
The Evolution of Primates

Economic bond among primates

In the family life-style of some primate is the creation of an ‘economic’ bond whereby males obtain food for females and their young.

As the attention of the mother is devoted to her young, she has less time to devote to obtaining food. Female primates, like all female mammals, nourish and carry developing young for many months before birth and also provide milk for the infant for months or years after birth.

Females need resources for themselves and their offspring, and makes can help acquire two of the main resources, food and safety.

For most primates, male contributions to female food supplies involve defending an area where food can be found. The females could spend less time searching for food and more time directly caring for and protecting her young.

The provisioning, bipedal male was able to obtain food farther away from the area occupied by the female and infant; thus, he increased their food supply without depleting local food resources.

But when male has exclusive sexual rights to a female (or group of females), this bond benefits both the female and the offspring because male provides food when necessary.
Economic bond among primates

Family structure of primates

One of the important aspects of social behavior in primates is the organization of some group in what might loosely be termed family structure.

Primates differ from other mammals in that they live in social groups based on the extended family. Within a group of primates, each individual recognizes the other members of its extended family and the entire extended family cooperates as a unit.

Studies of Hamadryas baboons in Ethiopia have shown that they do not live in promiscuous borders.

Although the troops might contain 60 members or more it is broken down into smaller family units, each with only one sexually active male and one or more females.

There seems to be no cross-mating among these family units. Studies of some other primate species indicate that they have similar family-like units.

Chimpanzees have strong emotional ties between members of a troop. Quarrels are rather frequent between these easily enraged animals but there is also marked tendency to settle such disputes quickly without asking questions of ‘guilt’.

A chimp after having been threatened or attacked by an animal of superior rank, ‘may follow the aggressor, screaming and crouching to the ground or holding out of his hand.
Family structure of primates