June 25, 2008 -- The phrase "blame it on the weather" takes new meaning in light of research suggesting that regional climate may very well have been responsible for the evolution of lifestyle, culture and even religion in the Middle East.
A new study published in the journal Antiquity marks the first time researchers have applied regional climate information to geographic variation in the Y chromosome (which only men possess).
"It is particularly exciting that climate may play a significant factor in the genetic patterns we see and, by extension, the long-standing cultural and lifestyle patterns of the Middle East," co-author Roy King, associate professor of psychiatry and behavioral sciences at Stanford University, told Discovery News.
He added that "climate, namely variations in rainfall" may have "influenced the development of the three major monotheistic religions of the Near East: Judaism, Christianity and Islam," but "to what degree" remains unknown.
What is known, based on the findings of King and his colleagues, is that before around 11,000 years ago, foraging groups gathered cereals and legumes, which grew naturally thanks to the wet winters and dry summers in the Fertile Crescent region.
Between 11,000 and 10,300 years ago, the region experienced a period of climate change, becoming colder and more arid.
The researchers took the climate data, focusing on annual precipitation, and compared it with Y chromosome information from databases that document men from Turkey, Egypt, Oman, Iraq, Jordan, Syria and the United Arab Emirates.
The scientists identified a genetic branch within the chromosome's genetic tree. Called "Haplogroup J," it, in turn, was split in two, with some individuals possessing a version called J1, others J2. The researchers found that J1 individuals were more likely to come from the drier regions and J2 men from the wetter parts of present day Turkey, Iran, the coastal Levant and Northern Iraq.
The subgroups corresponded to lifestyle as well as geography: The "wet weather" group consisted of agriculturalists, descending from the world's first known farmers. The men from drier areas were pastoralists, or semi-nomadic herders, with many traditions carried on today by Arabic Bedouins.
"The fact that we observe these differences now in living populations implies that cultural barriers to migration by males between settled agriculturalist and semi-nomadic herders may have been in place for a very long time," King said.
Prior work by the same team linked Y-chromosome data to the spread of Neolithic pottery and figurines in the Near East and southeastern Europe. The spread of material culture also matched the movements of the two basic groups.
Aaron Brody, associate professor of Bible and archaeology at the Pacific School of Religion, and director of the school's Bade Museum, told Discovery News that he read the new paper "with great pleasure, as it provides fresh data and insights into early settlement of the Near East."
"Given regional differences in the archaeological assemblage of Neolithic villages, it is fascinating to discover genetic links over the broader territory reconstructed from modern DNA analysis," he said, adding that the authors of the paper have provided a "fundamental map for bio-archaeology in the region."
In the future, King and his team hope to study mitochondrial DNA, which is passed down from mothers to their daughters, in the same region. He said women might have mixed more than men did between the farming and herding groups, but that is only speculation at this point.
Since climate change may have cemented the first Middle Eastern divisions, he also suggests concern over the possible impact of modern global warming.
"One wonders about the degree to which access to water for crops, and the changing climatic patterns due to global warming, might influence present and future conflicts in the region," he said.
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