The Marty McFly Problem, Part II in Whey and Sonic Screwdrivers.

Furthermore, something we take for granted in fiction. The same sperm and egg met.

Yes, yes, it’s fiction. But think about it. In most fiction where parallel universes meet, somehow, the same sperm and egg meet, time and time again.

So, let’s return to Marty McFly. Marty-A goes to the past and almost immediately starts perturbing it. Did the stress of seeing Marty-A effect Mom-B’s menstrual cycle? Did she eat differently? How were her emotions effected? WHEN DID SHE COPULATE WITH DAD-B? In other words, was the SAME egg released?

The same can be said for Dad-B. Did different swimmers make it into her vagina? DID THEY COPULATE AT THE SAME TIME AS THE PRIME UNIVERSE? What are the ODDS that sperm-B and egg-B are the same to create Marty-B? Odds are, Marty-B would probably be made of different gametes.

I think you see my point.

Want to kill Hitler? Just punch his dad in the balls the day before he’s supposed to copulate with Adolf’s mom. A different Adolf would be born. Maybe nurture would be the same. But definitely a different nature, even if similar. After all, brothers and sisters aren’t the same. Though, an alternate universe with an Adrian Hitler instead would have been… interesting.

Definitely would have set back the women’s movement, for sure.