Class 11 History
Beginning of Times
Fossil: The remains of very old plant or animal that have turned into stone are called fossil.
Species: A group of organisms that can breed to produce fertile offspring is called species.
The Precursors of Modern Human
- Primates emerged in Asia and Africa 36 million years ago.
- A subgroup amongst primates (called hominoids) emerged about 24 mya.
- The first hominids (human like creatures) emerged about 5.6 mya.
- The modern humans originated about 160,000 years ago.
|Smaller brain||Larger brain|
|Quadripedal locomotion||Bipedal locomotion|
|Less dexterity in hands||Greater dexterity in hands|
Evidence for African Origin of Hominids:
- It is the group of African apes that are most closely related to hominids.
- The earliest hominid fossils have been found in East Africa and date back to about 5.6 mya. In contrast, fossils which have been found outside Africa are no older than 1.8 mya. The earliest hominid fossils belong to the genus Australopithecus.
Hominidae: All forms of human beings belong to this family. Australopithecus and Homo are important genera of this family; apart from many other genera. Australopithecus has a smaller brain size, heavier jaws and larger teeth; compared to Homo.
Positive Feedback Mechanism:
Bipedialism enabled hands to be freed for carrying infants or objects. In due course of time, upright walking became more efficient. Bipedal walking also helps in conservation of energy because quadruped consumes more energy while walking. Bipedalism also increased the vision range of Homo species because the eyes were at a higher level. It helped in better visual surveillance. Once hands became free, they could be utilized to make tools. In turn, it also helped in increasing the brain size.
Effects of Climate Change: The Ice Age began around 2.5 mya. There were major changes in climate and vegetation. Temperature and rainfall decreased significantly. Grasslands expanded at the cost of forests. This led to gradual extinction of the early forms of Australopithecus. New species emerged which were better adapted to drier conditions. This was the time, when the earliest species of the genus Homo emerged.
The names assigned to the species of genus Homo are based on their typical characteristics. Some examples are given below:
- Homo habilis: The tool maker
- Homo erectus: The upright man
- Homo sapiens: The wise or thinking man
Fossils of Homo habilis have been discovered in Africa. The earliest fossils of Homo erectus have been found both in Africa and Asia. The fossils from Asia belong to a later date than those from Africa. So, it can be inferred that hominids migrated from East Africa to southern and northern Africa, to southern and north-eastern Asia, and perhaps to Europe; sometime between 2 and 1.5 mya. Homo erectus survived for nearly a million years.
In some instances, the names for fossils are derived from the places where the first fossils of a particular type were found. Some examples are given below:
|Homo heidelbergensis||Heidelberg (Germany)||Africa, Asia and Europe|
|Homo neanderthalensis||Neander valley (Germany)||Europe, western and Central Asia (disappeared abruptly in western Eurpoe around 35,000 years ago)|