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Comment by chris_wot | Hacker News Reader

There's a cheery thought!

Seriously though, what about if you marry someone from a different country? I'd imagine the chances are somewhat lower.

Never mind a different country - if you married someone from a different species they're still related to you. The only difference is the number of generations you need to go back to find the common ancestor.

Are we sure abiogenesis only happened once? Given how quickly life appeared once the conditions were right, it doesn't seem too implausible that the lightning strike might have happened in two different tidal pools on opposite sides of the planet, and it seems just vaguely plausible that there would be (bacterial) descendants of each that have no interbreeding in their ancestry.

I asked this in a thread on Slashdot once, and got a really good answer. Basically, there are a number of molecules that can have a left or right chirality. These happened by random chance at the beginning instances of abiogenesis, and were replicated faithfully since. So if it happened twice, a number of those molecules (or larger structures) would be backwards. From a macro perspective, things like the heart being on the left side, or the direction of other internal organs (i.e. appendix on the right side). At the molecular level, things like the spiral of DNA. There is some more information in Wikipedia, under abiogenesis and homochirality.

AFAIK all known life shares common ancestry. That doesn't mean life couldn't have arisen twice, but if it did, and if its descendants still exist, we haven't found them.

The chances of what? They are still your distant relative, like everyone on earth. Someone from a different country is probably more distantly related, but unless they're a humanoid alien, they're still related to you.

I guess there's not much point responding as the censor brigade came by and downvoted the hell out of my comment. It was a serious question, and I thank you for responding with a serious answer.

I don't think it was a censor bridge, it was a "this person didn't read the article" brigade. The point of the article was that everyone is related to everyone on a distant enough timescale. The person you responded to initially was making the point that everyone is your incredibly distant relative. Being in another country doesn't change that. 35 generations back, (mathematically) everyone has the same common ancestor.

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