A lesson in chewing coca   As a diversion during our four-day trek in search of fossilized dinosaur tracks and ancient rock carvings, our guides, Lucho (foreground) and Deli show us how to chew coca. The process basically involves cramming a cheek full of small and very dry leaves and slowly chewing them so that a trickle of bitter saliva trickles down your throat, preferably for hours on end.   Everyone in Bolivia does it, insisting that it gives energy and reduces the effects of altitude sickness. It is after all the leaf from which, with a lot of volume and effort, you derive cocaine. However I ascertained no benefits, only a mouth full of little green specks and stems, and a dry throat.           : Bolivia gallery : previous photo : next photo