Over the past 100 000 years or more, humans have migrated from country to country, spreading throughout the world. In the past, we have attempted to follow these trails by analyzing the radioactive isotopes found in human fossils, however, these remains are very rare and often incomplete and thus do not provide scienctists with all the information they need to have a clear understanding of our migration.
Our DNA however, which is nearly identical from person to person, contains telltale differences in a tiny .1 percent of it that has been proven to be able to assist scientists in their research. These special pieces of DNA remain unaltered as they pass from generation to generation thus becoming inheritable genetic markers. After a certain number of generations, this genetic maker is part of the DNA of Male and Female members of the area in which it arose. A comparison of this specific part of the DNA between people from all different races has been found to yield vital clues as to the progression of colonies from continent to continent. Now, instead of scientists only being able to analyze genetic footprints from father to son or mother to daughter, they inspect thousands of nucleotides spread throughout the genome.
The map you can see below represents some of the research from this widened field of study that have already resulted. The research interestingly shows proof of modern human origins in Africa having served as some kind of a pool of genetic diversity, which then proceeded to filter out throughout the rest of the world. Basically, a genetic branch with its roots beginning in Africa and stretching out to South American Indians and Pacific Islanders as its most recent branches. This is made quite clear by the migration lines starting if Africa and then moving out throughout the rest of the world.
In addition to human DNA indicators and to further assist scientists in replacing fossils with DNA, researchers have now found that they are able to search for patterns of migration within tiny microorganisms that have hitched a ride on humans during their migrations. Such organisms have included viruses, lice and especially bacteria among many others.
The Human Genome project, a project that has been running for the last 15 years that has radically changed the way we look at genes and has improved our abilities to harness information from them, has also significantly assisted scientists in tracing human migration. The project allows researchers now to look at the expanse of whole genomes amazingly in less than half the time and at less than half the cost.
With this new research, geneticists and scientists should be able to not only produce complete migratory maps, but also track human ancestry trees to fill in some of the questions about our history.
Link to main source of info: http://aguyinthepew.blogspot.com.au/2008/07/genetics-and-human-migration.html