beccaelizabeth (beccaelizabeth) wrote,

Portable gene scan for time travellers, with safety lock for their weapon...

today I discovered I did not understand as much as I thought I did about genetics and meiosis and recombination
which, given my a level grades, is not a surprise, but remains slightly frustrating.
but now I have a dozen tabs open to learn more and replace my wrong knowledge, which is always a nice opportunity.

... all this in aid of figuring out exactly how much of the world a time traveller from the 25th century would be related to, and how likely he is to grandfather paradox himself on accident if he's a serial killer.

... except the TV version of the flash says he's born 136 years into the future, which is a very different number of generations (and like 64 or 32 ancestors to memorise? 128 if all super eager?). And comics version gives multiple different dates of origin in quick succession according to web pages that claim to know, so who knows how many generations. so it's not entirely useful even in fanfic terms, it's just what I was wondering.

Because if you kill your grandfather you're clearly screwed, unless there was secretly a slightly different ancestry than you were aware of. But if you go far enough back we could have more ancestors than there were people, but don't because of marrying in your village and so forth, and people who do clever math reckoned an English child would be related to 80% of Britain a thousand years ago, or possibly not depending on which what where who and what you believe. So does that mean that a time traveller from far enough forward would have an 80% chance of a grandfather paradox if he killed any random person, or would it only matter if their specific genetics made it down the line to you?

But then that's more likely than I'd at first understood, because recombination, so you probably need a really large percentage of your ancestors for a bunch of generations. But there's one page has fancy graphs to show you're probably not related to all your ancestors at ten generations out. So could you just kill the ancestors you weren't carrying genes from, and because Time Wants To Happen, it'll all work out somehow anyway? Different ancestor swaps in instead, but washes out the same way? Seems unlikely.

Best just to say that time travellers trying to kill ANYbody far enough back they're unclear on their ancestry are risking a grandfather paradox, and that therefore time travellers should not dare be killers, and killers really must be stopped from time travel.

And it makes no sense to pack a ship full of vigilantes and murderers to go assassinate someone who started living four thousand years ago, and then treat their violence as trivial. It would be quite difficult to be sure of a four thousand year old man's descendants, even if he tried to keep track. And it would be impossible to be sure of the identities of all the people they've opened fire on, let alone their descendants.

Ciolence whilst time travelling is very likely to be terminally unwise.

Unless you are dealing with different species and an isolationist home planet, in which case you'd only have to make sure not to go home again. Unless of course you're a hybrid...

but, genetics. more complicated than I remembered even. which was quite complicated enough.

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Tags: meta, time travel
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