The Earth and Its People: The History of Human Evolution

Pages: 7 (1841 words) Published: January 31, 2012
I. African Genesis

A. Interpreting the Evidence

1. In 1859, Charles Darwin published On the Origin of Species, in which he suggested that species evolve over long periods of time through the process of natural selection. With regard to human beings, Darwin speculated that humans must be “descended from a hairy, tailed quadruped,” and that the process of human evolution must have started in Africa.

2. Discoveries of hominid skeletal remains on the island of Java (1891) and Beijing (1929) indicated Asian origins for human beings. However, the African origins of human beings were suggested by the discovery of Australopithecus africanus in 1924 and confirmed by the work of the Leakeys in eastern Africa beginning in 1950.

3. Archaeological evidence, understanding the evolution of other species, and tracing the human genetic code backwards has helped scientists track the evolution of human beings over a period of 5 million years.

B. Human Evolution

1. The australopithecines and modern humans are hominids, which are members of the primate family. Hominids such as australopithecines were distinguished from other primates by three characteristics: bipedalism, a very large brain, and a larynx located low in the neck.

2. Scientists theorize that these characteristics gave hominids advantages in the struggle for survival during the climatic changes of the Great Ice Age (Pleistocene period). Further climate changes 2 to 3 million years ago are thought to be the cause of the evolution of Homo habilis, whose brain was 50 percent larger than that of the australopithecines.

3. By 1 million years ago, Homo habilis and all of the australopithecines were extinct. They were replaced first by Homo erectus (1.7 million years ago) and then by Homo sapiens (400,000 to 100,000 years ago). Genetic evidence suggests that further development emerged around 50,000 years ago providing the capacity for speech.

C. Migrations from Africa

1. Both Homo erectus and Homo sapiens migrated from Africa to various parts of Europe and Asia; their migration was facilitated by the low sea levels associated with the Ice Age. Homo sapiens migrated from Africa during a wet period (40,000 years ago) and crossed the land bridge to the Americas during the last glacial period (32,000–13,000 years ago). The low sea levels associated with this period also allowed Homo sapiens to reach Japan and New Guinea/Australia.

2. These migrations were accompanied by very minor physical evolutionary changes such as changes in skin pigmentation. For the most part, however, humans adapted to their new environments not through biological evolution but through a process of technological adaptation.

II. History and Culture in the Ice Age

A. Food Gathering and Stone Tools

1. The period known as the Stone Age lasted from 2 million years ago to 4,000 years ago. It is subdivided into the Paleolithic (Old Stone Age—to 10,000 years ago) and the Neolithic (New Stone Age).

2. The Paleolithic age is characterized by the production of stone tools that were used in scavenging meat from dead animals and later in hunting. Homo sapiens proved to be particularly good hunters and may have caused or helped to cause the extinction of mastodons and mammoths about 11,000 years ago.

3. The diet of Stone Age people probably consisted more of foraged vegetable foods than of meat. Human use of fire can be traced back to 1.5 million years ago, but conclusive evidence of cooking (in the form of clay pots) can only be found as far back as 12,500 years ago.

B. Gender Roles and Social Life

1. The slow maturation rate of human infants and the ability of adult humans to mate at any time of the year are thought to be causes of the development of the two-parent family that is one of the characteristics of the hominids.

2. Researchers believe that in Ice Age society, women would have been responsible for gathering, cooking, and child-care, while men would have been...
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