Considering geological time as an important epistemological obstacle to the construction of ideas on biological evolution, a study was carried out on the so-called "Darwin Papers". The conclusion was that Charles Darwin's excursion in the Andes during March-April 1835 was a crucial step in this regard. An expedition was carried out in March-April 2002, in the exact same days of the year that Darwin had been there. The results of this expedition are described; these suggest a reappraisal of the traditional Darwin iconography and teaching strategies. (Contains 12 figures.)