In the lastest Antiquity project gallery, "fibre technology depicted in archaic art" is a re-interpretion of some rock art from Borneo, as depicting a twisted cord, presumably of some plant fibre, with frayed ends. The image is more than 8000 years old, and also includes human and apparent orangutan figures. Rather than being some sort of symbolic pathway, Judith Cameron, suggests that it represents something material, and she can point towards, admittedly later, evidence for plant cordage from Neolithic burials at Niah Cave. Of course, throughout the Palaeolithic, or at least the later Palaeolithic associated with modern human use of plant fibres, cordage, weaving of baskets must have been quite widespread. In addition to rare finds of actual cordage, such as at Ohalo 2 at >21000 years BP, other plant finds that suggest the use of plant cordage may be seen in the phytolith record: phytoliths of palms and from wild banana (Musa) leaves occur throughout the sequence at Batadomba-Lena rock shelter in Sri Lanka by to 36,000 BP [Perera et al. 2011 People of the Rainforest...]. And as phytolith sampling, and some exceptional examples of preservation, at Catal Hoyuk demonstrate there silica skeletons can provide evidence for Plants as material culture (Ryan 2011 in J. Anthro. Arch.), and so it is not too much of a strecth to think about phytolith, such as those from palms, Musa and many other fibrous monocots, as likely to represent past human gathering for raw materials, perhaps even more so than use as food.
One is reminded of Karen Hardy's impassioned plea for giving more consideration to the importance of string in early evolution on human technology ("String Theory" in Antiqiuty 2008). This reexamining of rock art appears to be step in that direction.