Science: History of Life on Earth: Major Events in the History of Life (For CBSE, ICSE, IAS, NET, NRA 2022)

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Major Events in the History of Life

  • Geological time scale: The time scale that includes the earth origin to present is called geological time scale. This age of the earth is divided into three eons they are as follows.
  • Phanerozoic Eon began about 570 million years ago, and it is still continuing a present. In this eon vertebrates and phanerogams are developed.

This eon is divided into three eras:

  • Cenozoic era: Cenozoic Era began about 65 million years ago and is still continuing. It is divided into two periods. Quaternary and tertiary. The wide variety of plants and animals that we know today came into existence during Cenozoic Era.
  • Mesozoic era: Mesozoic era began from 250 million years ago and ended at 65.5 million years ago. In this era, different types of hills and mountains were formed. It is supposed that the vital conditions for the survival of life on land, water and air were formed. This era is divided into three periods.
  • Paleozoic era: Paleozoic era was beginning from 540 million years ago and ended at 250 million years ago. In this era, the plants and animals were found to have developed which was found from the studies of the fossils remained in sedimentary rocks. Similarly, it is also believed that there was a change in atmosphere and whether. This era is divided into six periods.

Stages in Human Evolution

Stages in Human Evolution

The following are the stages of human evolution:

Dryopithecus

These are considered to be the ancestors of both men and apes. They lived in Africa, China, Europe, and India. The genus Dryopithecus means oak wood apes. When Dryopithecus was alive, the tropical lowlands which it inhabited were densely forested, so the members might have been predominantly herbivores.

Ramapithecus

Their first remains were discovered from the Shivalik range in Punjab and later in Africa and Saudi Arabia. They lived in open grasslands.

Two pieces of evidence confirm their Hominid status:

  • Robust jaws, thickened tooth enamel, and shorter canines.
  • Use of hands for food and defense, and extrapolations of upright posture.

Australopithecus

The Fossil of this genus was first discovered in 1924 in South Africa. They lived on the ground, used stones as weapons, and walked erect. They were 4 feet tall and weighed 60 - 80 pounds.

Homo Erectus

The first fossil of Homo Erectus was found in Java in 1891. These were named as Pithecanthropus Erectus. These were considered as the missing link between the man and apes. Another discovery made in China was the Peking man. This specimen had large cranial capacities and are believed to have lived in communities. Homo erectus used tools made of quartz. Tools made of bones and wood are also discovered. There is evidence of collective hunting՚s. There is also evidence of the use of fire. The Homo Erectus is believed to dwell in caves.

Homo Sapiens Neanderthalensis

The Homo Erectus evolved into Homo Sapiens. During evolution , two sub-species of Homo Sapiens were identified- Homo sapiens Neanderthal and Homo sapiens. The cranial capacity of Neanderthal grew from 1200 to 1600 cc. Few small hand axes had also been discovered. This species of hominids were capable of hunting big games such as mammoths.

Homo Sapiens

The remains of Homo Sapiens were first discovered in Europe and were named Cro-Magnon. In these, the jaws are quite reduced, the modern man՚s chin appeared, and the skull was rounded. Their cranial capacity was about 1350 cc. They gathered food through hunting. Art first appeared during this time.

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