When you mess up time travelling and become your own ancestor, there is a big problem:

At some point in time, a child will be born with exactly the same DNA as you.

Did any franchise address this problem? Because, as far as I understand, your descendants don't have your DNA.

So, as an example, you are your own grandfather.

  • You travel back in time with your DNA.
  • You "make" one parent of yourself with his or her own DNA.
  • Your parent "make" you and normally your DNA would be different thanthe one of all recent ancestors
  • 2
    – Valorum
    Apr 24, 2016 at 16:40
  • 1
    @Richard some people have weird fantasies xD
    – Armin
    Apr 24, 2016 at 16:44
  • 3
    Why would two people with the same DNA be a problem? Identical twins don't cause the universe to implode. Apr 24, 2016 at 17:33
  • @GeoffAtkins identical twins usually don't have the same dna. But after researching a bit, I learned that this difference develops after the birth. But only after John Sensebe's answer...
    – Armin
    Apr 24, 2016 at 17:36
  • This is essentially a "first of" question, although worded a little clunky. "First of" questions are on-topic.
    – user31178
    Apr 24, 2016 at 18:59

1 Answer 1


This is not, in fact, a problem. Your DNA is made up of bits of the DNA of your ancestors, but you might coincidentally share bits of DNA with other people outside of your family. Yes, there might be people out there, in distant lands, with your nose.

Taken to its logical conclusion, this means that by an amazing coincidence, there might be another person out there with the exact same DNA as you. Which makes it possible, however unlikely, that one of your own ancestors shares the exact same DNA, and you wouldn't even know it.

If that's possible and non-problematic without time travel, then why would it be a problem with time travel?

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