A new study charts the genetic family tree of the world's peoples
by Tamara Traubman
Researchers who analyzed the DNA of African men believe that they discovered a "genetic signature" belonging to the ancient ancestors of the human population.
The signature - which consists of a series of genetic changes in the Y chromosome that exists only in men - was found in some Ethiopians and in all the vaccinated. The Khoisani today live in the southern part of Africa and speak the Klik language - a language whose words are made up of "klik" sounds.
The head of the research team, Dr. Ornella Semino from the University of Pavia in Italy, said in an interview that she and her colleagues believe that the group of people in whom the signature was found may include direct descendants of the population of humanity's ancestors, who lived about 100 years ago in East Africa (including the area where it is today Ethiopia) and reached as far as South Africa.
The new findings, published in the January issue of the scientific journal "Human, Genetics" "The American Journal" complement previous research based on DNA found in mitochondria taken from populations all over the world. Mitochondria are structures in the form of tiny cylinders found inside the cell, and their role is to provide energy to the cell. But the DNA in the mitochondria has another feature, very useful in the effort to trace ancient genealogical lines: it is inherited only from the mother's side, to all her descendants - sons and daughters. Her daughters, in turn, will pass the mitochondrial DNA to their offspring, and so on.
Through the analysis of genetic changes that occurred over the generations in the mitochondrial DNA, it is possible to reconstruct the stories of the women in ancient times, and outline the family tree of their descendants. At the base of the tree are the ancient mothers of modern man, who first appeared in Africa about 150 thousand years ago. The branches branching off the tree represent their descendants, who left their place of residence and spread out into the world. A similar tree, which teaches about the history of men, can be built according to the genetic changes found on the Y chromosome. The deepest branches, located closest to the starting point, represent the populations closest to the ancestors of the human population.
Family trees drawn according to the mitochondrial DNA show that the earliest peoples are the Biaka (the pygmies in central Africa), and the Wasikla Kong, from the northwest of the Kalahari desert in Africa.
A family tree based on the Y chromosome was built by Dr. Peter Underhill from Stanford University in the USA, Dr. Semino and their colleagues, in a study published in November 2000. They discovered that the earliest mutations in the Y chromosome tree are found in the highest frequencies among the vaccinated, and among Oromo and Amhara in Ethiopia. The study published now is a continuation and expansion of the previous study.
Semino says that it is likely that many genealogical lines from the ancestral populations were lost, and those that remained, survived by chance. Therefore it is not surprising that the two trees - the one based on genetic changes in the mitochondria, and the one based on changes in the Y chromosome lead to different population groups. However, she points out that the two trees point to the Hussian, since the Vesicle Kong language belongs to the Hussian language family.
According to Underhill, "these early Y chromosome lineages are found today only in African populations, and appear to be associated with a hunter-gatherer lifestyle." Based on the assessment of the rate at which genetic changes accumulate on the Y chromosome, Underhill believes that the source populations began to spread to other areas within Africa 130 to 70 thousand years ago.
About 50 thousand years ago, a new genetic lineage appeared in Africa, whose population migrated to South Asia and Australia. And 30 to 20 thousand years ago, Underhill says, another dynasty arrived in Europe, originating from an Asian population.