I "Intelligently" merged a smaller gedcom from a relative in the last week. This was the first ttime I had done so. I expected this to do "what it said on the tin", but it has totally skewed my tree.  Apparently my name is now Sarah (I'm a man) and I was born about 50 years before my dad.

The question is:  Can I retrieve a previous tree to try and restore the original tree?  If not, this is going to take forever to fix.