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On priests and chromosomes

The discovery of the genetic similarity between the Lemba tribe from Africa and Jews is another layer in the understanding of the identity and difference of human beings

The discovery published at the beginning of the week, about the genetic similarity between the Lemba people in southern Africa and Jews of all denominations, surprised many and provided convincing proof of the origin of this tribe. It is difficult to understand how the immigrants went through such a big change in the "phenotype" - the set of visible features of the individual - while maintaining the characteristics of the "genotype" - the northern genetic markers in the DNA. It turns out that the gardens are a kind of "stored scrolls", and it is possible to read in them information that cannot be obtained through classical anthropology. And this is just the latest in a series of discoveries, in which modern molecular genetics makes it possible to closely follow the development of the human species and its migrations around the world, using DNA technologies.

Apparently a few Lemba people came from the Arabian Peninsula to South Africa about a thousand years ago. But if we turn our gaze to what happened in the region about 150 thousand years ago, we will find that there was then a migration of peoples on a much larger scale. Genetic discoveries in the last decade indicate that the intelligent human species, Homo sapiens, then migrated in the opposite direction - from Africa, through the Land of Israel, to Asia and Europe. This can be learned from a deep observation of the genetic characteristics of the people of the different continents today. This is done by investigating "difference markers", those points that have "text differences" in the DNA between different individuals within a certain species of animal or plant. Each of these sites is known as a polymorphism. They are responsible for all the differences between humans, from the shape of the nose and the color of hair and skin, to a tendency to obesity or asthma.

Between every two people of the same sex (male or female) there are about three million such differences. They can be discovered by "sequencing" the genes and used to diagnose diseases, determine parentage and criminal identification. One of the most intriguing uses of the various sites is in researching the history of humans and understanding our evolution from earlier species. This use is possible due to the existence of unique polymorphic combinations for entire groups and populations.

At first glance, it would be possible to guess that the genes of the brown-skinned Africans are considerably different from those of the light-skinned races of the other continents. But surprisingly it turns out that there is almost no genetic marker found in Europeans or Americans that is not found in Africans. On the other hand, there are certain versions of DNA sites found only in Africa. Based on these works, and with the help of mathematical analysis, it has been proven that all humans in Europe, Asia and the American continents are descended from a "subpopulation" that left Africa about 6,000 generations ago. It is speculated that the reason for this migration was a sharp increase in the life expectancy of this population, perhaps due to rapid intellectual development, and at the same time as the spread of the use of a spoken language. This was probably the event when the modern human species appeared.

When they left Africa, the members of the emerging new species met other human species, such as the Neanderthals. The intellectual advantage of the immigrants from Africa led to the rapid extinction of the members of the other sex. Israel is one of the only sites where proofs of the existence of Homo sapiens and Homo Neanderthals were found at the same time, and here struggles probably took place in which the former won. In this matter too, genetic research has recently contributed important information.

Through DNA sequencing, which was first extracted from the bones of a Neanderthal man from Europe, it was proven beyond any doubt that this is not only a different race but a separate species, that we are not his direct descendants. This finding strengthened the hypothesis of the African origin of the modern human species.

The use of DNA for the purposes of dating and understanding the difference between populations was made possible mainly by basing itself on unique regions in the genome. Most DNA fragments are mixed during sexual reproduction. For example, the "volume" of the genetic information, called chromosome 1 in our genomic "encyclopedia", consists of a mosaic of about a thousand sections, each of which we inherited from a different person from among our ancestors, who lived ten generations ago. This phenomenon makes it very difficult to analyze the comparative genetic results. The situation is different in the tiny DNA segment - the mitochondrial chromosome - which is inherited from the mother to all her offspring, without any contribution or interference from the father. DNA of this type was used for the first proof of the great African migration, and also for the study of ancient human bones. Bone identification in the criminal field also almost always relies on mitochondrial DNA, partly due to its much greater resistance to the ravages of time. But the man is not disadvantaged in the world of genes either. The Y chromosome, which is found only in men and contains the genes that determine the pair, is also resistant to mixing processes and is usually inherited in its entirety from father to sons. Because of this, Prof. Carl Skortsky of the Technion and his colleagues concluded that this chromosome would be passed on in complete inheritance in male lineages, such as in Jewish priests.

This hypothesis was adapted after a discovery that made waves among population genetics researchers about two years ago. The Y chromosome of priests often contains special versions of DNA markers, which hardly appear in other Jews or non-Jews. Confidence in this discovery was strengthened, when one considers the time that has passed since the priestly dynasty began and it turned out that the result fits well with the time of the Exodus from Egypt. These unique Y chromosome markers have now been found in a relatively high proportion also among the Lemba people, and especially among their religious priests, which led to the declaration of their Jewish origin.

In the coming decade, with the completion of the human genome project, the contribution of computational evolutionary molecular genetics to the understanding of man and his origin will greatly increase. It seems likely that all the millions of human sites of variation will be identified and documented. "DNA chips", iron or glass plates coated with DNA segments, which represent sites of variation, already today make it possible to carry out a computerized analysis of genetic differences.

In the near future, DNA chips will make it possible to create perfect genetic identity cards for every person. It will be possible to diagnose drug sensitivity, a tendency to cancer and cardiac arrest or even professional skills with the help of sophisticated genomic equipment. At the same time it will be possible to investigate in detail the migration of peoples, the formation of cultures and languages ​​and stages in the formation of the human species in the last millions of years. This is how we will understand, among other things, the appearance of the characteristics of the brain that distinguish us from the apes - thinking, language, science and art. We will fully know the difference between individuals, but we will also see a conclusive proof of the unity of all human beings - the absolute identity between all of us in 99.9% of the chemical letters, which are our genetic heritage.

One response

  1. If indeed all the priests are descendants of Aharon - how can one explain the light blue eyes and fair skin of Alfred Cohen and the Yemenite facial features of Saadia Cohen? Did many European and Yemeni women marry Jews?

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