The key to human evolutionary past lies in the genetics of Africa
For 200,000 thousand years humans have lived on the continent of Africa. Being the birthplace for all modern humans has allowed it to have the greatest genetic variation within our species.
The fields of genetics and genomics are rapidly advancing and the very recent analysis of thousands of samples from all over Africa have produced exciting results, helping to reveal the human evolutionary history of not only Africa, but of the world.
A recent article released in Science (May, 2009) presents the results of the team, led by evolutionary geneticist Sarah Tishkoff.
The genotyped DNA was sorted into closely connected and related groups or clusters, representing fourteen ancestral groups from which all populations today are derived. Promisingly the variations in the genes seem to correlate with different language, cultures and ethnicity around the continent.
Genetic diversity among human populations is at its greatest in Africa, where there has been longer opportunity for divergence. In addition genetic variance decreases as distance from Africa increases, providing evidence for the ‘out of Africa’ migration theorem. On analysis of patterns and similarities in the DNA, it appears that several great migrations occurred from various areas in Africa, particularly the East, backing up fossil evidence. A divergence around 18,000 thousand years ago (kya) resulted in a split between Eastern and Western pygmies. Another divergence approximately 15kya resulted in the Hadza and Sandawe linguistic groups, whom both originated with a ‘click’ language (Khoisan). A language that includes a series of clicks, similarly sounding to the noise riders make to encourage a horse to move.
It was discovered that many alleles of genes are found only in Africa, demonstrating the more complex evolution of the human race. As the population developed, so did their genes. Divergence led to a split between the genes, different alleles were carried with each migration, leaving a majority of alleles at the regions core.
DNA samples were also taken from African-Americans, representing another migration from Africa. Results showed that 71% of their DNA was from over Western Africa, 8% from other African regions and 13% from various European communities. These results suggest that the ancestors of African Americas are from all over, thus making it more difficult to track individual origins.
Understanding the population genetics of Africa will allow us to track and uncover humans evolutionary history. Uncovering human genetics allows for many great advances in understanding the behaviour and adaptations of our species. The research from this project will enable further discoveries by evolutionary and biomedical researchers, helping us to not only uncover our evolutionary genome, but to trace the relations between genes and the response to diseases.
For further information, please refer to the original article:
Tishkoff, S. Reed, F. Friedlaender, F. 2009. The Genetic Structure and History of Africans and African Americans. Science: viewed online 12 May 2009 <www.sciencemag.org/cgi/rapidpdf/1172257v1.pdf?maxtoshow=&HITS=10&hits=10&RESULTFORMAT=&fulltext=genetic+structure+and+history+of+africans&searchid=1&FIRSTINDEX=0&resourcetype=HWCIT>
