Ancient DNA teaches about the complex genetic history of the world's ancient farmers

In the earliest human DNA research in the Middle East, the cradle of the agricultural revolution, it was found, among other things, that the population of the first farmers in Israel developed here and did not originate from another ethnic group that migrated to the region and brought with it the secrets of agriculture

The earliest human DNA research in the Middle East, including sites in Israel, published today in the prestigious journal NATURE found that at the beginning of the agricultural revolution, about 12 years ago, there were three genetically distinct populations in the region: a population in Iran, a population in the Levant (Israel and Jordan ) and population in Anatolia (Turkey). "We knew that during the thousands of years after the beginning of the agricultural revolution there were many migrations in the ancient East and Europe, resulting in the creation of new genetically 'mixed' populations, but we did not know what was happening right at the cradle of the revolution - where and when it all started. Now we know, for example, that our ancestors, the local farmers, developed here in Israel, and they are not descendants of an ethnic group that comes from another region and brings with it the secrets of agriculture - as happened in Europe, for example," said Prof. Danny Nadel from the Zinman Institute of Archeology at the University of Haifa, one of the partners in the study.

It is known from previous studies that the agricultural revolution, one of the most important turning points in human history, begins in the ancient Near East - mainly along the fertile arc that includes the Jordan Valley - about 11,500 years ago. In a very short time, the agricultural revolution brought with it an abundance of food, considerable population growth and large waves of migration throughout the Eurasian space, which resulted in the fact that, similar to today, the populations of the region are no longer distinguished from each other genetically. However, until now almost nothing was known about the cradle of the revolution - about the initial period when certain societies began to domesticate plants and animals and develop agricultural technologies: did one genetic group develop agriculture and through migration transfer this knowledge to different places in the ancient East or did the idea and the practical details of the beginning of agriculture passed in some way between the different groups, almost without migration.

In order to get an answer to this question, genetic research was needed, but due to the hot climate of the Middle East, which resulted in very little preservation of DNA in ancient human bones, it was impossible to carry out such research until today.

All this until the current study, which was led by Prof. Ron Panhassi from University College Dublin and Prof. David Reich from Harvard, with the research group including Prof. Nadel from the University of Haifa, and Dr. Ward Ashad and Ms. Ahuva-Sivan Mizrahi from the Antiquities Authority. To overcome the difficulty of obtaining reliable DNA from such an ancient period, the researchers used new methods, such as a technique called in-solution hybridization that overcomes the ancient DNA contamination by bacteria. But more importantly, they chose to focus on ear bones which can provide up to 100 times more DNA than other body bones.

The combination of the innovative techniques allowed the research group to collect quality genetic information from 44 individuals who lived in the Middle East 14,000 - 3,400 years ago: hunter-gatherers who lived here before the transition to agriculture, the first farmers themselves and their descendants. Among the sites were Rakfat Cave in Carmel, excavated by Prof. Nadel and the human bones found there date back to 12-14 thousand years ago, with these skeletons actually being the oldest in this research and in the ZAT in general from which DNA was extracted. Another site from Israel (origin near Jerusalem, excavated by Dr. Ashad and Ms. Mizrahi) and sites from Jordan, Iran, Armenia and Turkey were included in the current study.

By comparing the genetic sequences to each other as well as to nearly 240 individuals who previously lived in nearby areas and about 2,600 people living today, the researchers learned that the first farming populations in the Levant, Iran and Anatolia were genetically different from each other - and very similar to the hunter-gatherers who lived there before. The difference was so great that the researchers defined the first three agricultural populations as "as different from each other as the populations of Europe and the Far East today". Also, while the separate genetic population in Anatolia was known, the study found for the first time that the Levant and Iran also had separate genetic groups during this period. This means that the initial spread of agriculture in the Middle East occurred mainly as a result of local inventions and the adoption of technologies from neighboring groups and not as a result of large migrations. But we do know that it passed with almost no immigration of people at this point," explained Prof. Nadel.

As mentioned, about 5,000 years later this genetic distinction disappears when the agricultural societies in the Mazat got mixed among themselves. However, the current study was able to continue to follow the groups of ancient farmers and see their genetic contribution to different regions of Eurasia: groups of farmers from the region of Israel, for example, spread south into East Africa. Farmers from the Anatolian group spread west into Europe, people from the Iranian or Caucasian group spread north into the Russian plains, and people related to farmers in Iran and hunter-gatherers from the aforementioned plains spread to South Asia.
Following the successes of the new genetic methods, Prof. Nedel believes that researchers will now delve deeper and deeper into earlier periods - including the periods when Homo sapiens and Neanderthal man lived together in the Land of Israel.