June 21, 2016
Study finds farming was invented in two places at once
A new study out of Harvard Medical School has found that, according to the genomes of 44 ancient Middle Eastern individuals, farming was actually invented twice—independently by two different groups.
Around 11,000 years ago, one of the most important revolutions in human history occurred: the Neolithic revolution, when our ancestors made the shift from hunting and gathering in nomadic groups to a more sedentary lifestyle. Early farmers were able to slowly domesticate a variety of crops and animals—which then led to their spread around the world about 9,000 years ago.And for a long time, the prevailing notion was that all of this arose from one place: the southern Levant region (which includes Israel and Jordan). Of course, dozens of studies have examined this idea, but the hot climate of the area makes it difficult to extract DNA from skeletal remains of the time period, meaning hard data is sometimes a challenge to come by.
Which is where recent advances paved the way for this latest genomic study, which can be found in a preprint on the bioRxiv server. As it turns out, scientists recently discovered that one particular bone in the body is extremely good at preserving DNA across millennia: a tiny ear bone known as the petrous. Thanks to this, Harvard researchers Iosif Lazaridis and David Reich were able to extract and analyze the genomes of 44 Middle Eastern individuals who lived 3,500 to 14,000 years ago.
The surprising development of farming
The results were a bit surprising. Two groups of Neolithic farmers emerged—one in the southern Levant, and another across the Zagros Mountains in western Iran—which had stark differences in their genetic makeup. In fact, the Zagros farmers were much more closely related to hunter-gatherers who had lived in the region before the Neolithic. Of course, in farming had started in the Levant and was transmitted as farmers spread from there, one would expect to find close similarities between the DNA of the Levant and Zagros groups—which clearly was not the case.
The researchers have taken this to signify, then, that farming did not develop in the southern Levant alone, but also independently developed in the Zagros region.
“There has been a school of thought arguing that everything happens first in the southern Levant and everyone learns how to be farmers from this initial dispersal,” said Roger Matthews, an archaeologist at the University of Reading, UK, who co-directs the Central Zagros Archaeological Project in Iran, according to Nature.
“But the archaeological evidence shows very strong local traditions that are clearly not in communication with each other, persisting for centuries if not millennia.”
However, there is a good likelihood that these independent farmers did not stay in separate bubbles, but actually mixed together genetically in eastern Turkey. From there, the farmers migrated to Europe, bringing their now-combined farming techniques with them. Others spread into what is now the Eurasian steppe, India, Pakistan, and East Africa.
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