Daffodil International University
Faculty of Engineering => EEE => Topic started by: Kazi Taufiqur Rahman on November 23, 2015, 11:43:49 PM
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Dogs first snuggled up with people in Central Asia. That’s the conclusion of a new study looking at genetic diversity in these popular pets. Earlier findings had suggested dogs were first tamed elsewhere.
Laura Shannon works at Cornell University in Ithaca, N.Y. As an evolutionary geneticist, she studies how traits in a species have changed over enormous spans of time. For the new study, Shannon joined an international team. “We have a large dataset,” she says, which allowed their team “to sample dogs from all over the world.”
In all, they looked at DNA from nearly 5,000 dogs. Most were purebreds. But more than 500 were free-roaming dogs living in villages around the world. Such “village dogs” make up the majority of dogs worldwide.
Dogs from Central Asia harbored the greatest diversity in their genes. “As you move out from Central Asia, we see a decrease in diversity,” Shannon says. That suggests people must have begun taming wild canines into pets near to lands now known as Nepal and Mongolia.
The researchers shared their findings October 19 in the Proceedings of the National Academy of Sciences.
Some genes in a starting species will be lost as animals are tamed, Shannon explains. Why? Only a fraction of the original group of tamed — or domesticated — dogs would have moved along with people to new areas. These dogs would have possessed just some of the genes present in the dogs they had left behind. Similar to how the neck on a soda bottle restricts the amount of liquid that gets through, the frontier dogs would bring only some of their community’s genes with them into a new area.
Earlier research had suggested that dog domestication occurred in a host of places. These included Europe, the Middle East, China, Siberia and North Africa. But many of these studies examined a limited type of genes. For instance, some looked at those in mitochondrial (My-tow-KON-dree-ul) DNA. These are genes that can be inherited only from the mother. Others looked only at the genes present as part of the Y chromosome that males get from their dads. Still other studies may have focused on autosomal (Aw-tow-SOAM-ul) DNA. This type holds genes other than those on sex chromosomes (the X or Y types).
The new study considered genes from each type of DNA, Shannon says. “That let us get the most complete picture we could.”
But these data all came from living animals. A lack of ancient DNA has led some critics to question the new study’s conclusions. Robert Wayne of the University of California, Los Angeles, is among them. Wayne, an evolutionary biologist, is concerned that this study’s findings don’t match up with those from earlier ones. Moreover, he argues that diversity patterns in living dogs might not be a foolproof map of domestication events in ancient times.
Ancient DNA could provide more insight into where wild canines were first tamed into dogs, Shannon agrees. Still, she believes, the new study will add to a global effort using many genetic techniques to investigate where the efforts to domesticate dogs and wolves first took hold.
Studying domestication patterns adds to the human story, too, she says. “Studying the history of organisms that we use and breed, and that we’ve had an effect on, tells us about history as well as culture and human migration.”
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Thanks for sharing