Saturday, February 03, 2018

History of the chicken

The Smithsonian Institution tells us that it is generally accepted that domestic chickens are direct descendants of the Red Jungle Fowl, Gallus Gallus of south east asia. The chicken’s star turn came in 2004, when an international team of geneticists produced a complete map of the chicken genome. The chicken was the first domesticated animal, the first bird—and consequently, the first descendant of the dinosaurs—thus honoured. The genome map provided an excellent opportunity to study how millennia of domestication can alter a species. In a project led by Sweden’s Uppsala University, Michael Zody and his colleagues researched the differences between the red jungle fowl and its barnyard descendants, including “layer breeds raised to produce eggs and broilers for eating. The researchers found important mutations in a gene designated TBC1D1, which regulates glucose metabolism. In the human genome, mutations in this gene have been associated with obesity, but it’s a positive trait in a creature destined for the dinner table. Another mutation that resulted from selective breeding is in the TSHR (thyroid-stimulating hormone receptor) gene. In wild animals this gene coordinates reproduction with day length, confining breeding to specific seasons. The mutation disabling this gene enables chickens to breed—and lay eggs—all year long. Once chickens were domesticated, cultural contacts, trade, migration and territorial conquest resulted in their introduction, and reintroduction, to different regions around the world over several thousand years. Although inconclusive, evidence suggests that ground zero for the bird’s westward spread may have been the Indus Valley, where the city-states of the Harappan civilization carried on a lively trade with the Middle East more than 4,000 years ago. Archaeologists have recovered chicken bones from Lothal, once a great port on the west coast of India, raising the possibility that the birds could have been carried across to the Arabian Peninsula as cargo or provisions. By 2000 B.C., cuneiform tablets from Mesopotamia refer to “the bird of Meluhha,” the likely place name for the Indus Valley Read more:

No comments: