Washington, Jan 07 (Agencies): Humans began to wear clothing 170,000 years ago, a technology which enabled them to migrate out of Africa successfully, a new study has claimed.

The evidence comes from seemingly very unfashionable lice, since US scientists tracked when head lice evolved into clothing or body lice 170,000 years ago, used DNA sequencing for their calculations.

"We wanted to find another method for pinpointing when humans might have first started wearing clothing. Because they are so well adapted to clothing, we know body lice or clothing lice almost certainly didn't exist until clothing came about in humans,"said study leader David Reed of Florida University.

The study shows modern humans started wearing clothes about 70,000 years before migrating into colder climates and higher latitudes, which began about 100,000 years ago, the 'Molecular Biology and Evolution' journal reported.

This date would be virtually impossible to determine using archaeological data because early clothing would not survive in archaeological sites.

"The study also shows humans started wearing clothes well after they lost body hair, which genetic skin-colouration research pinpoints at about one million years ago, meaning humans spent a considerable amount of time without body hair and without clothing," Reed said.

He added: "It's interesting to think humans were able to survive in Africa for hundreds of thousands of years without clothing and without body hair, and that it wasn't until they had clothing that modern humans were then moving out of Africa into other parts of the world."

Lice are studied because unlike most other parasites, they are stranded on lineages of hosts over long periods of evolutionary time.

"Applying unique data sets from lice to human evolution has developed within the last 20 years and provides information that could be used in medicine, evolutionary biology, ecology or any number of fields.

"It gives the opportunity to study host-switching and invading new hosts -- behaviours seen in emerging infectious diseases that affect humans," Reed said.

Ian Gilligan of the Australian National University, an expert, added: "It means modern humans probably started wearing clothes on a regular basis to keep warm when they were first exposed to Ice Age conditions."

The last Ice Age occurred about 120,000 years ago, but the study's date suggests humans started wearing clothes  in the preceding Ice Age 180,000 years ago, according to temperature estimates from ice core studies, Gilligan said. Modern humans first appeared about 200,000 years ago.

"The things that may have made us much more successful in that endeavour hundreds of thousands of years later were technologies like the controlled use of fire, the ability to use clothing, new hunting strategies and new stone tools," Reed said.