India, Aug. 29 -- Picture a prehistoric artist making markings in a cave. What do you see?

Most of us picture a man. But archaeologists in Europe are now concluding that, judging by the size of fingermarks and handprints, as much as 75% of that continent's cave art may have been created by women.

The history of bias in art goes all the way back, and most of us haven't yet switched to new ways of seeing.

Some museums are starting to make a concerted effort. And concerted it is, because somehow even art by women who were revered in their lifetimes has ended up forgotten in basements, or covered in mold in storage.

In Paris, London, Amsterdam, Venice in Italy, Vienna in Austria and Belgium's Ghent, archivists, curators and museum directo...