Evolution of Early Prosimians

Human Evolution of Class 12

Evolution of Early Prosimians

The Ancestral home of primates (not man) was the present continent of Asia, from where they migrated to three continent (South Asia, Africa and South America), due to increasing northern cold. In the order primates, man belongs to the suborder Anthropoidea, which includes monkey apes and man (Catarrhines). The other group of primates is prosimii, and it is believed that the earliest coenozoic prosimians including tree shrews, lemurs, loris and tarsiers gave rise to the higher primates including man.

Evolution of Anthropoids

The Anthropoids include the monkeys and apes, as well as human beings monkeys evolved from ancestral prosimians.about 3 million years ago when the weather was warm and vegetation was like that of a tropical rain forest. Old World Monkeys (Cercopithecoids) : Long non prehensile tail and flat noses, ground dwellers, e.g. Baboon, Rhesus monkey. New World Monkeys (Ceboids):- Short prehensile tail and protryding noses, e.g. spider monkey, organ grinder’s monkey (capuchin).

Hominoids

The hominoids include the apes and humans.

Apes:Gibbons, Orangutans, Gorillas and Chimpanzees. The earliest and primitive ape lived about 40 million years ago (oligocene) and is known as Parapithecus. It is believed to represent an ancestral stock from which all Hominoids (including human) have been derived. Another fossil Proliopithecus was found in Egypt and of early oligocene (38 to 25 million years ago) times. Proconsul is supposed to be an ancestor of the modern chimpanzee. By the middle miocene, a large group of apes, collectively called the Dryopithecus. Ranged through Africa in to Europe and Eurasia.

The Hominids

Humans and their close ancestors are called hominids. The first hominids probably emerged between 6-4 million years ago during the late miocene or early pliocene. The earliest known fossils (4-2 million years old) have been discovered in Southern and Eastern Africa. All hominids

had three features in common,

(i) Bipedalism   (ii) Omnivorous feeding behaviour   (iii) Further brain expansion and reorganization.

Man’s Place Among Mammals

Mammals evolved from primitive reptiles (therapsida) in Triassic period, about 210 million years ago. Mammals existed as inconspicuous group of small rat-like creatures for about 150 million years during Mesozoic era, diversification of mammals had taken place after the extinction of dinosaurs.

Order primate including man, great apes, monkeys, loris, lemurs and tarsiers originated about 65 million years ago during cretaceous period.

The anthropoid apes (ancestors of monkeys, apes and man) originated about 36 million years ago from Oligocene to Miocene epochs.

The hominids (ancestors of apes and man) evolved about 24 million years ago. Evolution of hominids took placed in Asia and Africa.

Sub-order Anthropoidea is also called Simians that includes new world monkeys; old world monkey sapes and man.

The Anthropoid apes or the ancestors of monkeys, apes and human evolved” about 36 million years ago and the hominids or the ancestors of Apes and humans evolved about 24 million years ago.

Today the Apes are represented by two families, namely Pongidae which include Chimpanzees, Gorillas and Orangutans and Hylobatidae which includes Gibbons.

Darwin (1871) put forwarded the theory of evolution of man form ape-like ancestors in his book Descent of man and selection in relation to sex. Carolus Linnaous named as Homo sapiensas wise man and placed them with apes and monkeys.

In 1863 T.H. Huxley first tried to explain origin of humans in his book “Man’s place in Nature”.

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