zoser, on 02 December 2012 - 08:42 AM, said:
Analogies will not solve this one. You can't cut large deep holes in granite with stone age tools without making an awful mess. The evidence in the above photos suggests that the feed rate was fast. Far too fast for a bow and string and faster even than we could do (see Dunn's analysis).
[...]
Hogwash.
Three men (two pushing/pulling bow at the rate of 120 revolutions/min, and one holding 2.5 kg capstone)

(
Experiments in Egyptian Archaeology: Stoneworking Technology in Ancient Egypt, Denys A. Stocks, Taylor & Francis e-Library, 2004, page 132)
in 20 hours drilled 6 cm deep hole in
red granite using
copper tube 8 cm in diameter, and 1 mm thick walls (it is argued, that more experienced workers could drill that hole in 10 hours)

(
Experiments in Egyptian Archaeology: Stoneworking Technology in Ancient Egypt, Denys A. Stocks, Taylor & Francis e-Library, 2004, page 133)
And
similar "grooves", or striations, you mentioned,
were seen on the hole wall (as well on the column wall) after drilling.
zoser, on 02 December 2012 - 08:42 AM, said:
[...]Further a close up of the Inca relics reveals to be that the stone has somehow been burned; inside is a darker colour that then outside if you look closely.
Hmmm... As far as I know, Incas knew fire.