Finger on Mars confirms ancient civilizations?

This is an image taken by curiosity's mast cam.

The image captures what looks like a finger with nail. The rovers wheels are 750mm wide, a human finger is about 90mm.....the finger appears to be roughly 80-120mm in length.
(Taking into account perspective)

Is this part of an old statue depicting humans??? The scale and detail lead me to believe this may well be the case. The finger looks to be rock, that is why i think it is part of a statue.



Source: rob19791