Back to basics
The thesis begins with an excellent introductory chapter that reviews the background literature in an intelligent, scholarly and accurate manner. The candidate takes a commendable 'back-to-basics' approach, reviewing some of the very early (and indeed seminal) papers in the field that are now often (regrettably) overlooked.
It's certainly true that examiners scrutinize your bibliography carefully. It's also true that they particularly notice if the bibliography does not include recent work. Often examiners will comment that there is nothing cited past a certain date - say 2002. They rarely comment if there is nothing before a certain date, but they do notice when original work is cited. Going back to original sources is a sign of high quality scholarship, and it can often lead to new interpretations of that original work which were missed at the time it was being read by other scholars.
The earliest reference in my thesis was to a book published in 1932. What's your earliest reference?