Homo sapiens: Out of Africa
By the time the most advanced species of modern
man, Homo sapiens, had evolved, about 120,000 years ago, there is evidence of
rapid population growth around the globe. So how did Homo sapiens spread?
While it is generally accepted that the forerunner to Homo sapiens - Homo erectus
- left Africa about 1.5 million years ago to populate other parts of the world,
there are two main theories about the spread of Homo sapiens.
The first theory, known as the 'Out of Africa' model, is that Homo sapiens developed
first in Africa and then spread around the world between 100 and 200,000 years
ago, superseding all other hominid species. The implication of this argument
is that all modern people are ultimately of African descent.
The other theory, known as the 'Multi-regional' Model, is that Homo sapiens evolved
simultaneously in different parts of the world from original Homo erectus settlers.
This means that people in China descended from the Homo erectus population there, while Australians may have descended from the Homo erectus population in South East Asia.
Both theories have their staunch defenders who cite DNA evidence - analysis of the genetic blueprint passed down from generation to generation - to advance their case. Out of Africa theorists, for example, say that most genetic variation in human populations is found in Africa, suggesting that humans have evolved there for the longest period.
Although the debate is far from concluded, it is probably fair to say that the bulk of scientists support the 'Out of Africa' hypothesis and believe that all humans share a common origin.