Her larger theme is to warn against the "it's been done" effect, a mindset that can infect whole research communities as well as individuals. "It's been done" says, for instance, that a colored spot on a geologic map says everything worth knowing about a place and that new mapping would be a waste.
One thing Eliot implies is that "where we started" was itself the beginning of a journey. Therefore you keep exploring, and each time you return to the start you know something new for the first time. You never know a place for the last time. And another corollary is that even if "it's been done" by someone else, it hasn't been done by you. And if you value your own curiosity, you won't mind looking into things that have "been done" if it means you will know them for the first time.
Serpentinite on Ring Mountain Geology Guide photo