Human Evolution | NEB Class 11 Biology

CHAPTER 7.4 Human Evolution

Origin and Evolution of Man

To find out the origin and evolution of modern man i.e. Homo sapiens sapiens many an anthropologist has been made the vast study. The fragmentary fossil records available so far suggest that men have arisen in the plains of Asia, Africa and Europe from some non-human or apes like forms which lived 20-24 million years ago.

Evolutionary Trend

• It is the general pattern of change of organisms from their ancestral states.
• The human evolutionary changes are as follow:
  • loss of opposability of great toes
  • Erect posture by development of lumbar curve
  • Increase in the size and complexity of brain.
  • Development of chin

Evolutionary Time Scale

The fossil records suggest the men and modern apes had a common ancestor known as Hominids. It is presumed that hominids existed 24 million years ago.

1. Gibbon diverged from the main lines about 10 million years ago.
2. Orangutan diverged from the main lines about 8 million years ago.
3. Human evolved about 2.3 million years ago.

Ancient Human Fossils

• The fossils of Ramapithecus, Sivapithecus and Australopithecus are considered as the ancient human fossils. These fossils are assumed to be originated from a common ancestor for the origin of both apes & man i.e. Dryopithecus or Proconsul.

1) Ramapithecus

• It is considered as the direct ancestors of man.
• These include a curved jaw with an arched plate.
• It may have lived in Nepal about 11 million yrs ago.

2) Australopithecus

It is the first human like form which existed about 1.25 million years ago in the dry land of South Africa.

• Brain capacity was 600 c.c.
• They walked upright and showed more similarity to man.
• They probably weighed about 40-50 kg.
• They are about 4-5 ft tall.

Modern Human Ancestors

The earliest ancestors belonging to the genus Homo is considered as modern human ancestors. A number of species belonging to the genus Homo have been recognized from the fossils records. These are:

1) Homo habilis

• It existed about 2 million years ago.
• Its fossils were recorded from East Africa.
• It lived in the open grassy land and was omnivorous.
• The cranial capacity was about 700 cc.
• It used tool for hunting and defense.

2) Homo erectus

• It is the earliest fossils existed about 1.7 million years ago. Two similar fossils were recorded from Java and Peking about 50000 yrs ago and are supposed to belong to the same species. Homo erectus.

Java man

• Its fossils were recovered by Dubois in 1891 from Eastern Java.
• It existed about 50000 yrs ago.
• It had the cranial capacity of about 600cc.
• It was more than 5 feet tall and weighted nearly 70 kg.
• They might have constructed and used tools and also learned to light fire.

Peking man

• Its fossils were recovered by W.C Pei (1924) from caves near Peking in China.
• It was very similar to the Java man.

3) Neanderthal man

• Its fossils were found in Neanderthal valley of Germany
• Its cranial capacity was almost similar to modern man (1450cc)
• Its brain was almost as large as modern man.
• They made tools for hunting and defense

4) Cro-Magnon man

• The fossils of Cro-Magnon were first discovered in rock at Cromagnon in France in 1968 by Mac Cregor. It is modern man called Homo sapiens, which was evolved about 40000-50000 yrs ago. Its characteristics:
  • The cranial capacity was 1600cc
  • They were about 5 feet tall
  • The forehead was broad and had raised narrow nose and prominent chin

Homo sapiens sapiens (modern man)

• It is supposed that today's modern man has evolved from Cro-Magnon man about 10 thousand years ago in the region around Caspian Sea in central Asia. Then they migrated in three directions.

1. Westwards: Present days white race found in Europe, south west Asia and North Africa.
2. Eastwards: They changed into present day's Mongoloid race in China and Siberia.
3. Southwards: They changed into present day's Negroid race found in India, South Africa and Malaysia. However, the origin and evolution of man might have occurred from ape like ancestors.

Difference between Apes and Man

Difference between New world monkeys & Old world monkeys