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The Daily Mail says:

A 12-year-old girl created family tree linking 42 of 43 U.S. presidents to King John of England, who signed the Magna Carta in 1215. Only the eighth president, Martin Van Buren, was not related to John.

This has been recently spreading on news web-sites and Facebook, especially by conspiracy theorists.

Is this true?

Sklivvz
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Noam
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    Here's the conspiracy theory aspect: The [Most Royal Candidate](http://en.wikipedia.org/wiki/Most_royal_candidate_theory) theory suggests the candidate with the closest ties to European royalty is always elected, thus proving that election results are organised by the Illuminati... – Oddthinking Aug 12 '12 at 11:53
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    It's interesting that people believe this, but this is [The Daily Mail](http://www.youtube.com/watch?v=5eBT6OSr1TI) we are talking about! – JMK Aug 12 '12 at 20:07
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    If on average every descendant has 1.5 children who have descendants in turn, and a generation is 20 years, then John would have more than 600 million descendants by now... – hdhondt Aug 13 '12 at 00:21
  • @hdhondt But every inbreeding event cuts a branch ... :D – Dr. belisarius Aug 13 '12 at 05:36
  • That's why I did not make it an answer. I'm sure this is the reason, but I don't know which assumptions to use. While inbreeding cuts branches, most people also had way more than 4 kids, as well as more than 1.5 producing offspring. I just picked some numbers that sounded not too far out. If someone can put some real numbers in this, it would make an answer. – hdhondt Aug 13 '12 at 11:14
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    This is similar to a question I asked some time ago about whether [all the presidents were descended from George Washington](http://skeptics.stackexchange.com/q/7344/1792). – Brian M. Hunt Aug 14 '12 at 04:34
  • This story [dates back to at least 2010](http://www.santacruzsentinel.com/ci_14408412) – Oliver_C Aug 14 '12 at 11:00
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    6 degrees of Francis bacon... – Chad Aug 15 '12 at 01:48
  • A bunch of European royality had the right of the first night. They could also rape women without negative consequences for themselves, especially in wartime. Those relations won't show up in official family trees but I would suspect that all Americans of European descent are related to King John of England. – Christian Aug 15 '12 at 13:25
  • What I have difficulty believing is that the genealogy of all those presidents is known that far back. 1215 is a heck of a long time ago (especially for Americans!) – Benjol Aug 17 '12 at 09:15
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    @Christian Wikipedia is somewhat sceptical of those claims being the case in Europe: http://en.wikipedia.org/wiki/Droit_du_seigneur – Andrew Grimm Aug 17 '12 at 13:27
  • @Sklivvz My deleted answer may not give a yes/no answer, but it does specifically address this part of the question: "is there a statistical explanation that makes this more likely than it seems?". My answer is a clear "yes" to that. – hdhondt Aug 20 '12 at 23:46
  • @hdhondt that part of the question is leading and off-topic. Thus I am editing it out. Furthermore, your maths is off (but math discussions are off topic here, so I will only elaborate in the [chat]). – Sklivvz Aug 27 '12 at 02:30

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