Evolution of Human

Last Updated on Monday, 23 January 2012 03:43 Written by Sandesh Monday, 24 May 2010 04:43

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Origin and Evolution of Human

Human belongs to an order Primata of the class mammalia. Primates also include Tarsiers, Lemurs, Lorises, Monkeys and Apes. Primates occurred some 60 million years ago during the tropical climates of Paleocene and Eocene epoch of Cenozoic era. The first primates were terrestrial, insectivorous and shrew-like.

Characteristics of Order Primata:

1. Grasping limbs- opposable thumb with grip for power
2. Rotating forlimb- hand can rotate through 180o
3. Stereoscopic binocular vision- eyes close together on face with parallel optical axes
4. Enlarged skull
5. Large forebrain
6. Few offsprings
7. Only one pair of mammary gland in female.
8. Nails are present instead of claw

These primates evolved into two sub-orders Prosomii and Anthropoids.

Sub-order 1: Prosomii includes:

1. Tarsioidae (includes Tarsier)
2. Lemuroidae (includes Lemur and Lorises)

Tarsiers are small primates with large eyes, reduced snout, long feet and long tail. Their feet have extremely elongated tarsus bones, which is how they got their name. They are nocturnal animals. They are primarily insectivorous, and catch insects by jumping at them. They are also known to prey on birds and snakes and have excellent huntings. Tarsiers are now only found on several Southeast Asian islands including the Philippines, Sulawesi, Borneo, and Sumatra.

Lemurs are also small tree living primates. They have long bushy tail, small eyes and long snout. They are found in Madagascar Island

Sub-order 2:  Anthropoids include New world monkey, Old world monkey, Apes and Human.

Anthropoid ancestors diverged into 3 families:

1. Cebidae which includes New World monkey or Platyrrhini (eg. spider monkey)
2. Cercopithecidae which includes Old World Monkey or Catarrhini (eg. baboons and proboscis monkeys)
3. Hominoids which includes apes and human.

All New World monkeys differ slightly from Old World monkeys in many aspects, the most prominent of which is the nose. This is the feature used most commonly to distinguish between the two groups.

The scientific name for New world Monkey, Platyrrhini, means “flat nosed” Therefore they have flat nose with widely separated nostrils. They have prehensile tail which are capable of holding objects with their tails. Limbs are not used for grasping objects by new world monkey. For eg. Spider monkey

The Old World Monkey, catarrhini, in contrast have narrow nose with closely placed nostrils. They have non-prehensile tail which is not capable of holding objects. But, they use their limbs for grasping. For eg. Rhesus monkey ( Macaca mulata)

Human and their ancestors are more closely related to apes than other anthropoids and apes in turn are more closely related to Old World Monkeys than New world monkeys.

It is generally accepted that the ape-human ancestors diverged from that of monkeys some 25-30 million years ago in Oligocene period of Cenozoic era. Similarly, the seperation of apes and human ancestors occurred between 5 and 10 million years ago in the middle of the Miocene period.

Hominoids further diverged into two super-families:

i.        Pongidae: includes Apes likes Gibbons, Orangutang, Gorillas and Chimpanzees.

ii.        Hominidae: include modern human and their fossil forms.

Apes are mostly semi arboreal in nature. Gibbons ( genus Hylobates) are small apes while Gorilla and chimpanzee (genus Pan) and Orangutan (genus Pongo) are large and heavy. They have grasping arms which are longer than their limbs.

Ape and human have some common characteristics like:

• Absence of tail
• Larger head, brain and cranial capacity
• Broad chest
• Capable of sound production
• Developed facial musculature for expression ( like surprise, pleasure etc)
• Menstruation in female

Due to these similar characteristic features apes and man are presumed as cousins.

Later in the miocene period, apes started to evlove into human. Fossils of prehuman ancestors are obtained from Africa, Asia and Europe. This indicates that main centre for origin of man was probably Asia and Africa. During Pliocene period there was continental elevation in Himalayas due to movement of Indian plate towards Chinese plate. This caused increased aridity of climate in northward of Himalayas or Tibetan region. As a result, the forest in these area degraded and there was effect on tree dwellers. Now, they had to come down from trees on land. On ground they were in secure from other predator animals like Tigers and bears. They acquired adaptations necessory to ensure their survival like use of forelimbs for protection and walk in two legs called as bipedalism. These changes brought the initiation of human evolution.

Trend in Evolution:

1. Bipedalism and errect posture: The common ancestors of human and apes were likely to have used all four limbs for locomotion, something like chimpanzee. But during the course of evolution there was the development of upright posture i.e. bipedalism. The bipedalism resulted in the freedom of hands from locomotion. This enabled our ancesctors to use their hands for carrying objects and manipulating environments. They acquired more errect posture with development of lumbar curve from ‘C’ shape to ‘S’ shape.
2. Increase in size of brain and intellegence: Development of bipedalism was followed by the changes in nervous system which resulted in the increase in size of brain and intellegence.
3. Became hunter: Loss of easily obtainable food from forest due to its degradation, man became hunter.
4. Reduction of eye brow ridges: The eye brow ridges became reduced.
5. Development of chin: their chin became prominent.
6. Changes in diet: There were also changes in diet. From fruits, hard nuts and tough roots to softer food including an increasing dependance on meat. This involved decrease in size of the tearing and biting incisors and cannines. Later, when human learned to make fire and cook food, there was decrease in the size of teeth.
7. Ability to communicate: There was articulation of speech and increase in ability to communicate with others. This led to develop organized community behaviour.
8. Clothing: They learned to wear cloths made up of animal hides and fur to survive in extreme cold.

Fossil Records:

Ancient Human Fossils:

The fossil records show the appearance of many ape and human-like hominids in the process of formation of modern human from apes. These are:

1. Ramapithecus:

The first incomplete fossils of Ramapithecus were discovered by G. edward lewis of North India in 1932. They included jaws and teeth. It is believed that they inhibited the tropical and semitropical areas of earth some 14 million years ago.

In Nepal, a tooth belonging to Ramapithecus has been found near Tinau Khola, a couple of miles near Butwal. Ramapithecus is the earliest fossil primate which scientist believed to be a direct ancestor of man.

2. Shivapithecus:

Fossil remains of Shivapothecus were found in the Siwalik Hills of India and Pakistan in 19^th century. The fossil records of this genus dated from 12.5 million to 8.5 million years old in the Miocene. Their skull bore many similarities with that of orangutangs and thus they are considered to be closely related to orangutangs.

3. Australopithecus:

Australopithecus or “South african apeman” are the forerunners of man. The first fossils of Australopithecus were discovered by Raymond Dart at Taung, South Africa in1924. The fossil records suggested that they evolved in Africa over 4 million years ago i.e. in between Pleistocene and Pliocene period. Australopithecus show remarkable man-like and ape-like characteristics.

• They were believed to be skillful runners and stood erect most of the times.
• They were 1.20 m tall.
• Their cranial capacity was about 600cc. which is larger than that of ape but smaller than that of human.
• They had large jaws and teeth.
• They had prominent eye-brow ridges and underdeveloped chin.
• They used primitive stone tools for hunting.

Two species of Australopithecus are known, A. africanus and A. robustus. The fossils of the former one are smaller and look more like ancestor of Homo sapiens.

Modern Human Fossils

During the early Middle Pleistocene, from about 800,000 to 500,000 years ago, men existed which formed transition between australopithecines and Homo sapiens.

1. Homo habilis:

Homo habilis is the first species of the genus Homo, evolved in South and East Africa in the late pliocene. Its fossils were discovered by Louis Leaky in Tanzania in 1964. He nick named this man as “handy man”.

• H. habilis lived for about 2.4 to 1.5 million years ago.
• They were 1.2 to 1.5m tall and weighed 40-50 kg.
• They had small molars and larger brains than Australopithecines.
• They had a cranial capacity of 660cc.
• They made tools from stone and perhaps animal bones.
• They lived in open grassy land, walked errect and were omnivorous.

2. Homo erectus:

The first fossils of Homo erectus were discovered by a Dutch physician, Eugene Dubois on 1891 on the Indonesian Island of Java.

• H. erectus lived from about 1.8 MYA to 700,000 years ago.
• They are the first human ancestors to walk truly upright.
• They made tools out of stones and hunted in well organized manner.
• They were believed to have used fire to cook meat.
• It is also beloved that they possessed prImitive form of speech.

Two examples of H. erectus are known. They are:

a) Java Man: Java man was one of the first specimens of Homo erectus to be discovered. It was discovered by Eugene Dubois in 1891 from rocks in central Java. It was originally named as Pithecanthropos him. They were about 1.5 m tall. They walked erect. They had the cranial capacity of 940cc.

A second Java Man was later discovered in the village of Sangiran, Central Java, 18km to the north of Solo in 1969. Their brain size was about 1000cc. The fossils of second Java man was found to be 800,000 years old.

b) Peking Man: Peking Man (sometimes now called Beijing Man), is another example of Homo erectus. The remains were first discovered in 1923-27 during excavations near Beijing (Peking), China. The finds have been dated from roughly 250,000-400,000 years ago.

The Peking man was similar to Java man. It had underveloped chin but developed eye-brow ridges. Its cranial capacity was about 1075c.c

3. Neanderthal man ( Homo neanderthalensis):

The Neanderthal man (Homo neanderthalensis) was a species of the Homo genus that inhabited Europe and parts of western Asia. It was discovered by Fuhlrott in 1856 in limestone cave in the Neander valley, Germany. It is one of the best known fossil men.

• Neanderthal man appeared some 350,000 years ago and disappeared 24,000 years ago.
• Their cranial capacity was about 1450c.c, as large as that of modern human.
• They had many adaptations to a cold climate, such as large braincase, short but robust builds, and large noses — traits selected by nature in cold climates.
• On average, Neanderthal males stood about 1.65 m tall (just under 5′ 5″) while females were about 1.53 to 1.57 m tall (about 5′–5′2″).
• Males were heavily built, and muscular due to their physical activity and robust bone structure.
• Evidences suggest that they are much stronger than modern humans.
• The tools used by Neanderthals were made up of stones which very well-fashioned.
• They walked in a stooping fashion.
• They used animal skin to cover their body and also knew how to make fire.
• They buried their death which shows that they had the knowledge of rituals.
• The Neanderthals were very violent in nature and often exhibited cannibilism.
• They were capable of communicating with each other by some sort of language.
• They had developed a primitive sort of social life.

4. Cro-magnon man ( Homo sapiens fossalis): (cro=cavity, magnon=large)

The first fossils of Cro-Magnon man were discovered by the geologist MacGregor in 1868 in the Cro-Magnon rock shelter of France. The rock shelter contained a large cavity which protected the fossils.

• Cro-Magnons lived from about 40,000 to 10,000 years ago.
• These people were anatomically modern, only differing from modern humans by their slightly more robust physiology and larger brain capacity.
• Their cranial capacity was about 1600c.c, which is slightly larger than that of modern man. Therefore it is believed that they were more intelligent and cultured than modern man.
• They had a diet of meat, grain, wild carrots, beets, onion, turnip and other foods. All together they had a very balanced diet.
• Males were about 1.8 m in height while females were about 1.60 m.
• They could walk and run faster and lived in families in cave.
• They used bones as weapons.
• The remains of tools suggest that they knew how to make woven clothing.
• They had huts, constructed of rocks, clay, bones, branches, and animal hide/fur.
• These early humans used manganese and iron oxides to paint pictures.

Cro-magnons developed in Asia and Africa and invaded Europe. It is believed that Cro-Magnon was responsible for the disappearance of Neanderthal man.