The Domestication of Barley

According to an article on Science Now barley has been domesticated at least twice. The problem is that early evidence for domesticated barley occurs in two areas. The Fertile Crescent around 10,500 years ago and in Central Asia around 9,000 years ago. Complicating the picture is the fact that:

Today, the wild progenitors of domesticated wheat and other founder crops grow only in the Fertile Crescent, but wild barley is found in the western and eastern regions. As a result, archaeologists haven’t been sure whether the cultivated barley in the east came from the Fertile Crescent or was domesticated directly from local wild plants.

To answer the question researchers sequenced the genes from wild and domestic barley in both areas:

They focused on seven genes that differ slightly according to the plants’ geographic origins. The genetic variations in the eastern domesticated samples much more closely resembled those in the wild plants from the east than those in wild plants from the Fertile Crescent, they report online this week in the Proceedings of the National Academy of Sciences. Morrell and Clegg conclude that barley was domesticated at least twice, first in the Fertile Crescent and then between 1500 to 3000 kilometers further east in Central Asia…

The research is being published in PNAS and the abstract (I don’t have access to the entire article) paints a somewhat different picture of the findings:

Genetic diversity for each population was calculated by using Nei’s diversity index, and a Spearman rank correlation was carried out to test the association between gene diversity and 16 ecogeographical factors. Highly significant correlations were found between diversity at the Isa locus and key water variables, evaporation, rainfall, humidity, and latitude. The pattern of association suggests selective sweeps in the wetter climates, with resulting low diversity and weaker selection or diversifying selection in the dryer climates resulting in much higher diversity.

Which makes me think the question of the origin of domesticated barley may not have been the main focus of the research.
Incidentally, check out Razib’s post on agriculture.

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