The only natural key a human being will normally be able to follow is their DNA, and I still think chimera-ism or tissue donation or other genetic anomalies might make even that inconsistent.

Most natural keys that identify dimensions of your data are slowly changing anyway - an address isn't a permanent fixture of a building, an area code splits, nations go to war, daylight savings changes on a whim, laws change, rules change, our understanding of the universe changes.