A team of scientists has successfully sequenced 6,000-year-old barley grains, the oldest plants sequenced to date, and deduced that domestication of the grain began in northern Israel.
The 6,000-year-old seeds were found in an exceptionally inaccessible cave 100 meters below the lip of the ancient Masada fortress, near the Dead Sea. Given that reaching it involves climbing down a sheer cliff face, the Yoram Cave most likely served as somebody’s prehistoric refuge rather than a regular residence thousands of years ago. The extreme aridity of the area was invaluable to the preservation of the grains over millennia.
For the scientists' investigation, each seed was cut in half. One part was used to date it using the carbon-14 method and the other was pulverized for genetic sequencing.
The ancient barley was compared, morphologically and genetically, with 137 traditional strains of the grain and 113 modern ones collected throughout the Fertile Crescent. Doing that enabled the international team of researchers from Israel and Germany to draw the barley family tree. That is how they reached the conclusion that the site of initial domestication, the smoking cookpot as it were, lay in the Upper Jordan Valley and Upper Galilee in northern Israel.
Until now, examination of ancient plants has been limited to looking at them and searching for differences between them and present-day specimens.
“Our analyses show that the seeds cultivated 6,000 years ago greatly differ genetically from the wild forms we find today in the region,” says Nils Stein, who directed the comparison of the ancient genome with modern genomes at the Leibniz Institute of Plant Genetics and Crop Plant Research in Germany, with help from the Scotland's James Hutton Institute and the University of Minnesota. “This demonstrates that the domestication of barley in the Fertile Crescent was already well advanced very early,” he said, referring to the region stretching from present-day Iraq and Iran through Turkey and Syria into Lebanon, Jordan and Israel.
The results of sequencing the Chalcolithic-era seeds show them to be genetically very similar to present-day barley grown in the Southern Levant, says the team in their paper, published today in Nature Genetics.
Other finds, such as the earliest known flour-making and baking equipment found nearby, support these theories. Large stone mortars from around 12,500 years ago were evidently used to make barley flour, which may have been baked into an early form of bread.
Will move continents, won’t bring food
“For us, ancient DNA works like a time capsule that allows us to travel back in history and look into the domestication of crop plants at distinct time points in the past,” says Johannes Krause, director of the Department of Archaeogenetics at the Max Planck Institute for the Science of Human History in Jena, Germany, which handled the actual sequencing process.
Barley was key to prehistoric man living in the Levant as he transitioned from a life of hunting and gathering to one of settlement and farming over 10,000 years ago, though the process may have been choppier than previously assumed. (For instance, a giant village dating back some 12,000 years was discovered in northern Israel, casting doubt on previous theories about the transition.)
In any case, the ability to domesticate, plant and grow food — as opposed to wandering about in small groups hunting and eating animals — was central to the process of settlement, which culminated in the development of civilization as we know it.
Among other plants that prehistoric man in the Levant domesticated were wheat, peas, lentils, chickpeas and flax, all of which remain local staples to this day.
The research on the ancient barley genome was led by Prof. Ehud Weiss of Bar-Ilan University with Prof. Tzion Fahima of the University of Haifa. They worked with teams that included people from the Hebrew University of Jerusalem and the Max Planck Institute in Germany.
The barley grains the scientists sequenced were grown thousands of years after the domestication process began. It is known that both wheat and barley were already being grown over 10,000 years ago in the Fertile Crescent. “It was from there that grain farming originated and later spread to Europe, Asia and North Africa,” says Fahima.
The grains had been found in 2009, together with tens of thousands of other plant specimens, in a dig managed by Dr. Uri Davidovich of Hebrew University and Nimrod Marom from Haifa University. Weiss led the archaeobotanical analysis.
One surprise was the similarity between the ancient barley and the modern domesticated lines in the region. “This similarity is an amazing finding considering to what extent the climate, but also the local flora and fauna, as well as the agricultural methods, have changed over this long period of time,” says Martin Mascher of the Leibniz Institute of Plant Genetics and Crop Plant Research, the lead author of the study. The researchers suspect that immigrants and conquerors coming to the Levant did not bring crop seeds from their former homelands. They simply kept growing the local landraces — the barley lines grown here all along.