The timeless desire to leave ones stamp on another artisan's work ...
Here is a 150 year old engraving left on the beautiful rocks at Karnak
And at Abu Simbel (Bottom right corner of the image.. on Ramses forearm)
600 AD Roman grafitti in the temple of Philae
1799 graffiti left by the French army
And probably the most famous (and deplorable) of them all .. by Belzoni in Khafre's pyramid
I found a web-site Graffito Graffiti dedicated entirely to graffiti's on the Egyptian and Sudanese monuments.