There are very few things that make my brain go WTF and do flip flops, However a discusion over on
bipolypagangeek is doing just that. the conumdrum is posted thus ...
'An interesting question that came up while writing a short story:
If a future version of yourself traveled back through time to meet you, would you have sex with them? If you did (like my character does), would you use protection?
Let's say that you get tested regularly and your future version knows all your tests in this time period are negative. And lets assume that you trust yourself to be ethical enough that you don't think your future self would lie or manipulate you here.
I suppose it's possible that you have something that didn't show up on your tests. And while you'd both have the exact same strain, your future self might have a more advanced form that could be transmitted to you.
It's also possible that your future self has something that they don't know about yet.
But the paradoxes are the part I don't have figured out. I don't think it would be possible under these circumstances to transmit something to your future self. But if your future self could transmit something they just picked up to you, wouldn't that have shown up on the tests your future self knows about? If they passed an advanced form of something to you, would that change the health status of your future self? Would that happen before your eyes? Would their new health status impact you again? Who knows some good time travel theory?
The end result, I'm guessing is that the risk is probably lower than unprotected sex with people who aren't future versions of yourself. I could see being tempted to declare a fluid bond with yourself, but I don't think the risk wold be zero.'
Its .. some what *um* Bizarre (not to mention just wrong on sooooo many levels)...