Two papers have come out this week that refine our understanding of the agricultural revolution in the Neolithic Near East. The first is actually an advance copy, “Population Based Re-sequencing Reveals that the Flowering Time Adaptation of Cultivated Barley Originated East of the Fertile Crescent,” published in the journal Molecular Biology and Evolution, in which the researchers sequenced 184 samples of the Ppd-H1 gene of barley.
Ppd-H1 is a circadian clock gene, one that affects variation in flowering time. The authors identified a unique haplotype due to a SNP called SNP48, which causes early flowering in long days. Specifically a cytosine at SNP48 is associated with early flowering in long days, whereas a thyamine at SNP48 is not associated with early flowering in long days. Effectively this SNP allows for the plant to grow where the growing season is short and with a dry summer. Early domesticators of barley would have selected for this SNP to create a more versatile, flexible barley crop.
They next sought to identify where this SNP originated from. So they did a phylogenetic analysis of the Ppd-H1 gene and traced down the origins of domesticated barley to Iran. Here’s the unrooted tree:
A Phylogenetic Tree of the Barley Ppd-H1 Gene
Is this surprising? No, it is not. 8,000 year old sites in Iran like Ali Kosh have yielded evidence of domesticated barley. And if you’ve ever had ash-e jo, an Iranian barely soup — you’d know the Iranians and barley have had a very intimate history. But, this finding is extremely fascinating because it correlates a phenotype with artificial selection that can be traced to the region of the world where it originated from.
While we’re discussing domestication cultures in the Middle East, a new paper has come out in the journal Nature which extends the domestication of cattle by 2,000 years earlier than previously thought. I must disclaim that I haven’t read the full paper, because my VPN access to my institution’s library seems to be broken, so I’m running this summary off this National Geographic news article. The paper, for those with access, is “Earliest date for milk use in the Near East and southeastern Europe linked to cattle herding.”
This paper is based upon a chemical analysis of 2,200 milk jugs from sites across Turkey, southeastern Europe, and the Middle East. 8,500 year old vessels from northwestern Turkey have high levels of milk fat embedded in the walls. Lead author, Richard Evershed, thinks that cow herders in northwest Turkey were the first milk users, but not necessarily drinkers, because the jugs indicate that they were used to store butter, yogurt, or cheese. Furthermore, the lactose tolerance genotype didn’t appear until 7,000 years ago — 1,500 years after these jugs were being used. Ultimately the significance of this is that people were herding cattle for their milk and using it indirectly — processing milk way before for lactose intolerance problems were resolved.
Jones, H., Leigh, F.J., Mackay, I., Bower, M.A., Smith, L.M., Charles, M.P., Jones, G., Jones, M.K., Brown, T.A., Powell, W. (2008). Population Based Re-sequencing Reveals that the Flowering Time Adaptation of Cultivated Barley Originated East of the Fertile Crescent. Molecular Biology and Evolution DOI: 10.1093/molbev/msn167