Oligocene Epoch Essay

Its common knowledge that the most primitive mammals appeared nearly 200 million years ago. That remote geological epoch is known as the Age of Reptiles. Gradually all primitive species renovated, some of them died out, others turned into absolutely new ones. At the end of Eocene epoch species were enriched by two new primates. An early stage of primitive evolution is characterized by several changes: brains enlarged while head became smaller, upper extremities learned to move faster, claws were replaced by flat nails.

Next geological epoch of Oligocene is known for appearance of new live of primates, which were divided into branches: New World monkeys (Ceboidea), Old World monkeys (Cercopithecoidea) and hominoid (it included present-day human, gorilla, chimpanzee, orangutan and gibbon).

One of the most important discoveries of this period is considered to be Parapithecus, found in Egypt. Some anthropologists consider that creature of this kind was an ancient ancestor of hominoids. Others exclude even the connection between Paraphytecus and primate. Though it is difficult to define exact gender of Parapithecus, it is extremely important as it may make clear the lineal origin of humans.

Speaking about Oligocene it’s important to mention discoveries in Europe and Africa at this period. They included Propliopithecus and Prohylobates, both of them were found in Egypt. Pliopithecus came from France and Limnopithecus was discovered in Kenya. The majority of specialists keep to the point that even though these fossils couldn’t be human ancestors, they were more or less similar to modern gibbons. However, they also resembled present-day primates in a number of features. Oligocene epoch lasted for about 13 million years. Researchers however are not able to find out exact period of time. Nevertheless it is quite obvious that Oligocene epoch was a period of adaptive division of anthropoids.

Oligocene is the last epoch of the paleogenic period. It is supposed to start nearly 40 million years ago. It is preceded by the epoch of Eocene.

Researchers consider that there were several adaptive radiations of primates. The third considerable adaptive radiation is supposed to take place between Eocene and Oligocene. As a result of this period new supreme anthropoids appeared on the Earth. These were groups of primates, which were a mixture of present-day species of monkeys and human. Along with many extinct forms of creatures those primates combine features of platyrrhine and narrow-nosed monkeys. The boundary between Eocene and Oligocene is characterized by essential changes of climate and fauna. At the end of Eocene there was an exchange between Asian and Northern American fauna. By this time continental links between Europe and Northern America were finally cut off. However there still existed a land bridge between Asia and Europe, which caused essential changes mainly in fauna of European continent — nearly 60% of existed forms were renovated.

The ancient representatives of primitive anthropoids were discovered in the Eocene sediments in Birma. They are defined by incomplete lower jaws and possess features of half-monkeys and anthropoids especially in dental structure. Oligocene primates were also found in Egypt. These appeared to be anthropoid race of Aegyptopithecus, Propliopithecus, Parapithecus, Apidiun, Oligopithecus and Quatrania. Nowadays the majority of anthropologists consider them being representatives of monophyletic group. However some researchers presume that their ancestors are of “adapid” origin. But these days there are not so many supporters of this theory.

As it was mentioned ancient primates were defined by fragments of lower and upper jaws. According to many evidences, Egyptophytec and Propliophytec are primitive forms of platyrrhine, narrow-nosed monkeys. By skeleton structure Egyptophytec is similar to Pliophytec.

Parapithecidae is a group of monkeys, who are considered to live in the upper Eocene and lower Oligocene of Egypt. Fayum contains a great number of amazing fossils. Few of them have already been found. Parapithecus and Apidium are among the most famous. Apidium are the most primitive representatives. They resemble platyrrhine monkeys in many ways, mostly by dental structure. Apidium were hardly taller than a usual squirrel. They used to live on trees, eat fruits and insects.

Another kind of Parapithecus is known as Propliopithecidae, which occupied the same territory in Egypt. They are represented by Algeripithecus, Aegyptopithecus and Propliopithecus. On the whole they are quite similar to Parapitecidae. Moreover these primates include subfamilies of Propliopithecinae among hominoids. Their size varied from marmoset to that of a macaque. They used to move on all fours, which are supposed to be “seizing”.

After a period of about 40 million years, which is generally accepted to be an evolutional gap, genealogy continues with species found in Egypt. On of them is Aegiptopithecus. It’s hard to define their forerunners, as nothing is known about the period before. However some specialists claim that they were ancestors of ancient driopithecus. Aegiptopithecus is a fossil monkey, living nearly 30 million years ago. Unlike other ancient primates resembled anthropoid apes. They are probably ancestors of proconsul and are distinguished as early hominoids. As a possible ancestor of present-day monkeys, Aegiptopithecus has short acoustic duct, small brains and not very big frontal lobe. In general they resemble lower primates.

Propliopithecus as primitive hominoids included Aegiptopithecus and Eolopithecus. They were discovered in Southern America: first in Bolivia and Argentina, later — in Texas. Evolution of American Propliopithecus took place in isolated conditions, being rather monotonous (mostly among trees).

In the course of time more and more researches have been made, trying to complete the family tree of humans. But as time passes more and more mysteries appear in the way to truth.