ERODE, January 29: Historical evidence pertaining to the deep roots of the bonded labour system in Tamil Nadu has been unearthed. The Kongu Research Centre here has collected palmleaf records of the practice going back to the 19th century. Aristocratic families of the area used to keep men and women, either individually or in groups, as slaves, and also engaged in buying and selling these labourers, according to the palmleaf manuscripts.