According to Wikipedia:
"Ascending and Descending" is a lithograph print by the Dutch artist M. C. Escher which was first printed in March 1960. Escher said there are 'free' people and these recalcitrant individuals refuse, for the time being, to take part in the exercise of treading the stairs. They have no use for it at all, but no doubt, sooner or later they will be brought to see the error of their non-conformity. Escher suggests that not only the labours, but the very lives of these monk-like people are carried out in an inescapable, coercive and bizarre environment. Another possible source for the people's looks is the Dutch idiom "a monk's job", which refers to a long and repetitive working activity with absolutely no practical purposes or results, and, by extension, to something completely useless.
* Wikipedia: Ascending and Descending http://en.wikipedia.org/wiki/Ascending_and_Descending