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I think it depends a bit on how you count but I've heard it is an 8 holed donut

It also differs between individuals (e.g. one can develop a fistula).

Or get a piercing.

So getting pierced, puts one topological outside of baseline humanity?

I suppose it does. Be careful, you wouldn't want to end up homeomorphic to the wrong crowd.

Aren’t tattoos injective?

When two artists do each other's backs, bijective.

If I met a 8 holed donut I'd tear it a new one.

I expect I'd start by tearing it one fewer: now a seven holed donut with some stubs.