Scientists use retroviruses to unravel woolly history of sheep domestication

Apr 24, 2009
Scientists use retroviruses to unravel woolly history of sheep domestication

(PhysOrg.com) -- Scientists at the University of Glasgow have unravelled the woolly history of sheep domestication by examining retroviruses preserved in the animal’s DNA.

Livestock domestication, which was a fundamental step in human history, occurred approximately 11,000 years ago in Southwest Asia before spreading to Europe and the rest of the world.

Originally, were used primarily for their meat, but up until now it was not known where selection for secondary products like wool first took place. Also, no genetic marker was known to differentiate primitive breeds from modern ones.

However, a study led by Professor Massimo Palmarini, a virologist from the Faculty of Veterinary Medicine of the University of Glasgow, published in the , suggests that most likely, breeding of sheep for products such as wool also occurred first in Southwest Asia before spreading to Europe through secondary migrations that shaped the great majority of present-day sheep.

In coming to their conclusions, scientists examined the presence of a particular group of endogenous retroviruses (enJSRVs) within the DNA of 1,362 sheep from 133 different breeds of domestic sheep and their closest wild relatives.

Endogenous retroviruses are like genetic fossils; remnants of ancient infections caught by sheep and their ancestors thousands of years ago whose DNA has been integrated into the of the animal and then passed on to subsequent generations.

The sheep were tested for the presence of six enJSRVs and by comparing the prevalence of the different viruses amongst the sample group Prof. Palmarini and his colleagues were able to differentiate primitive breeds from the more recently domesticated animals.

The tests revealed that sheep previously recognised as primitive - such as the Soay sheep of St Kilda and the Orkney sheep in Scotland for example - were among some of the very first domesticated sheep. Other primitive breeds include the Mediterranean Mouflon and some sheep breeds present mostly in Scandinavia.

Interestingly, the Orkney sheep are more closely related to Nordic breeds in Scandinavia while Soay are linked to Mouflon, providing intriguing insights into ancient routes. Thus, primitive breeds were generally found on the periphery of Europe or in isolated areas.

Prof Palmarini said: “The primitive breeds survived the second migrations of improved breeds from Southwest Asia by returning to a feral or semi-feral state in islands without predators or by occupying land less prone to commercial exchanges.

“Most, if not all, of the breeds we identified as being of ancient origin were already considered primitive due to traits such as a darker, coarser fleece, moulting coat and presence of horns even in females.”

Scientists say that similar tests used in the study could be applied to other species and be used to identify and preserve rare primitive breeds of animals.

Prof Palmarini added: “By being able to differentiate primitive breeds from modern ones our study offers a rationale for identifying and preserving rare gene pools. We have also demonstrated how ERVs can be used as a new class of genetic markers to unravel the history of a domesticated species.”

The study involved scientists from twenty different countries including Dr. Bernardo Chessa, Prof Tom Spencer at Texas A&M University, and Dr Ingrid Mainland, an archaeologist at the University of Bradford. This work was primarily funded by the Biotechnology and Biological Research Council and Wellcome Trust.

More information: The paper ‘Revealing the history of sheep using retrovirus integrations’ is published in Science. http://www.sciencemag.org/cgi/content/abstract/324/5926/532

Provided by University of Glasgow

Explore further: Certain virus-derived genomic elements have now been shown to actively regulate important developmental processes

add to favorites email to friend print save as pdf

Related Stories

New tool to fast-track genetic gain in sheep

Jan 14, 2009

(PhysOrg.com) -- Scientists from CSIRO are part of an international team that today launched a new genomic tool which is set to transform the future selection and breeding of sheep around the world.

Study discovers secret of Scottish sheep evolution

Jan 17, 2008

Researchers from the University of Sheffield, as part of an international team, have discovered the secret of why dark sheep on a remote Scottish Island are mysteriously declining, seemingly contradicting Darwin’s evolutionary ...

Wanted: A sheep in sheep's clothing

Jun 06, 2006

Australian scientists say they are looking for the ugliest merino lambs they can find in a study that may challenge the dominance of synthetic fibers.

Recommended for you

Crowdsourced power to solve microbe mysteries

2 hours ago

University of New South Wales scientists hope to unlock the secrets of millions of marine microbes from waters as far apart as Sydney's Botany Bay and the Amazon River in Brazil, with the help of an international ...

Reading a biological clock in the dark

23 hours ago

Our species' waking and sleeping cycles – shaped in millions of years of evolution – have been turned upside down within a single century with the advent of electric lighting and airplanes. As a result, ...

User comments : 0