|Calister, Jeffrey C. Brief Review in Earth Science. Englewood Cliffs, NJ: Prentice Hall, 1993: 188-189, 242-243.||"Humans like mammals have existed on earth for a relatively short time -- only about 0.04% of the earth's existence."||1,800,000 years
(0.04% of 4.5 billion)
|The World Book Multimedia Encyclopedia. New York: World Book, 1996.||"Most anthropologist believe that between about 400,000 & 300,000 years ago, Homo erectus evolved into a new species called Homo sapiens."||400,000–300,000 yr|
|Boaz, Noel T. & Alan J. Almguist. Biological Anthropology: A Synthetic Approach to Human Evolution. Englewood Cliffs, NJ: Prentice Hall, 1997: 380.||"Asia fits into a framework of world wide appearance of Homo sapiens at about 500,000 years ago."||500,000 yr|
|Leakey, Richard E., and Roger Lewin. People of the Lake: Mankind and its Beginning. New York: Anchor Doubleday, 1978: 252-253.||"The basic grade of Homo sapiens was probably around half a million years ago."||500,000 yr|
|The World Book Multimedia Encyclopedia. New York: World Book, 1978.||"Most scientist believe that Homo erectus developed into the species Homo sapiens between about 400,000 and 300,000 yrs ago."||400,000–300,000 yr|
|Lewin, Roger. New Scientist. 19 July 1997: 5.||"The results support the 'Out of Africa' model of human evolution. This holds that the modern human physique first appeared in Africa about 150,000 years ago, and then spread into the rest of the Old World, replacing existing populations of archaic human forms."||150,000 yr|
The main trend that I have come across while doing this research is that the values given reflect the hierarchical nature of evolution. The Genus Homo appears first around 1,800,000 years ago. The species Homo sapiens appears first around 500,000-300,000 years ago. The subspecies Homo sapiens sapiens appears first around 150,000 years ago. Every source gave its answer as a time period or estimated length of time. Every source gave its answer as a time period or estimated length of time. Each source did agree on the era. The Quaternary era also known as The Age of Man is this period. On the geological scale this is the last and most recent era. The Quaternary is divided into two smaller time periods called Holocene (or Recent) and Pleistocene epoch -- ten thousand years ago and 1.7 million years ago, respectively. The consensus is that Homo sapiens originated sometime during the Pleistocene.
The method used to determine man's age is by dating the fossilized bones of the Homo sapiens found at archaeological digs. The encyclopedia gives the value as being between 300,000 and 400,000 years old for the origination of Homo sapiens. Another reference just uses the Pleistocene epoch as the period, and then categorizes certain fossils as lower, middle or upper Pleistocene. By dating the fossils you get the age of the fossil. Scientists separate early hominids into Homo erectus, Homo habilis, Homo sapiens and Homo sapiens sapiens
Scientists have identified the skeletal structures of Homo sapiens in different parts of the world. The main conroversy centers around the question of whether Homo sapiens evolved from a single population in Africa or simultaneously in different parts of the world. Some evidence (molecular genetics) supports the "Out of Africa"model, other evidence (morphology) supports the "Multiregional Evolution"model.
Troy Holder -- 1997