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If we don't know who the author is, we don't know who the copyright-holder is.
If we don't know who the author is, and when the work was created, and under what circumstances (these are the source data), then we can't know the copyright status. We can't know what licenses, if any, apply to the work. Of course, sometimes the rules change if the author was never really known – and if the work is old enough the author does not matter. The "old enough" varies by jurisdiction and circumstances; you can ask for help at the Helpdesk.
We have a mandate only to provide works that are known to be available under a free license (or in the public domain). That is, works that are known not to infringe on the copyrights of any author.
Therefore, works with unknown author or copyright status (license), will necessarily be deleted. Please don't upload them to Wikimedia Commons.