new delhi the freezing caves on an isolated stretch on the lehmanali route some 4000m above sea level look anything but hospitable the path itself is treacherous cutting through mountains amid glaciers but part of one that connected ancient india to china and central asia the silk route that traders travellers and pilgrims took this route has been known for years what isnt known is how they survived ita study by geochemists from the birbal sahni institute of palaeosciences in lucknow may have found the answer in a maze of interconnected caves beyond the last pass before leh near the rumtse sasoma sumdo gya and meru villages in the ladakh valley scattered across these caves about 812 feet high and 10 feet wide are traces of life broken pottery diyas and the key to their findings sootit seems the caves have been in use since before the 11th century dr anupam sharma lead author of the paper published in the journal of archaeological science reports by elsevier told toi the caves were used intermittently by travellers and transhumant communities those who move with livestock seasonally to look for summer and winter pastures mostly in summer but they could have been in use throughout the year because they are relatively lowlevel and close to streamsladakh had been the convergence point between central and south asia when the silk route was thriving the 60day journey on the ladakh route linking amritsar northwest india and yarkand southwest china on the silk route southern branch was routinely employed by merchants until the late 18th19th century when mainland borders between india and china were closed for strategic reasons the paper said coauthor dr amritpal singh chaddha added the himalayan economy was dependent upon its trade with central asia and chinaevidence of human presence in these areas itself is not new the tibetan plateau had been occupied by prehistoric human ancestors by the neolithic age the agriculture phase of human evolution which began about 12000 years ago and archaeological traces of the earliest habitation in the region go back even further to the last glacial maximum about 22000 to 18000 years ago but winters are excruciatingly long and the mountains remain snowcovered for three to four months in a year the air is thin there is barely any rain and vegetation is restricted to the valleys alone not the easiest place to call homebut we found soot on the roof of the caves these go back to the 17th18th century in discussion with other scholars it is believed that it is the last known date up to which the caves were used by humans sharma said the ladakh samples suggest wood was burnt inside these caves depositing a hard sticky shiny and resinous black charred material on the roof such coatings may be the result of a condensed smoke generated by fire based activities cooking and heating most likely to maintain habitable conditions inside the caves the paper said additionally the use of