Wikipedia:Reference desk/Archives/Humanities/2024 June 19

Welcome to the Wikipedia Humanities Reference Desk Archives
The page you are currently viewing is a transcluded archive page. While you can leave answers for any questions shown below, please ask new questions on one of the current reference desk pages.

June 19

What proportion of people in the world have less than 127 different persons within the 7 consanguinities?

A person, his/her parents, his/her grandparents, his/her great-grandparents, his/her great-great-grandparents, his/her great-great-great-grandparents, and his/her great-great-great-great-grandparents, with 7 consanguinities, adding up to 2^7-1 = 127 different individuals, a person usually has 127 different persons within the 7 consanguinities, but some person has less than 127 different persons within the 7 consanguinities (this is because consanguine marriage), what proportion of people in the world have less than 127 persons within the 7 consanguinities? Also, what is the minimum number of persons within the 7 consanguinities such that there is a known person (may be in history) to have? 218.187.65.229 (talk) 02:54, 19 June 2024 (UTC)

There is an article in the German WP, de:Ahnenschwund, which traces geneaologies of selected royalties for >7 generations. Estimating any average may be impossible, as such documentation is only available for a few notable individuals. --Cookatoo.ergo.ZooM (talk) 07:55, 19 June 2024 (UTC)

OMG, that's so not true. We have nearly all the family trees of everybody on Iceland going back to 874. See deCODE genetics. Abductive (reasoning) 09:14, 19 June 2024 (UTC)

Iceland is, compared to continental Europe, a total exception to mobility. Numerous wars and migratory shifts have resulted in the loss of documentation on the European mainland. There is no point in extrapolating from a sample of 1 which is not representative. --Cookatoo.ergo.ZooM (talk) 10:40, 19 June 2024 (UTC)

Nonsense. People choose mates the same way, mobility up to about 1850 was low worldwide, and all OP wants is an estimate. Abductive (reasoning) 19:07, 19 June 2024 (UTC)

• UK:
• Celtic population
• Roman legions in England
• Viking incursions, South and East
• Anglo-Saxon settlement in England
• Viking era under Cnut the Great
• Norman Conquest
• Great Fire of London
• Emmigration to US and other colonies
• Blitz Krieg
• Immigration from (previous) colonies
• Immigration of EU labour forces

• Iceland
• Population = Natfari and 2 slaves in the 9th century
• Settlement by Old Norse and Gaelic groups, 874 AD
• No wars
• No conquests

• That Icelanders are the same species is a profoundly irrelevant and idiotic comment. That mobility (on the continent) was low until 1850 is total rubbish. --Cookatoo.ergo.ZooM (talk) 17:08, 21 June 2024 (UTC)

• It's you who don't get it. Everyone alive today who is of European heritage is descended from everybody alive in Europe in the year 800. Why? That was 48 or so generations ago given a 25 year generation time, meaning that you theoretically have 281,474,976,710,656 ancestors from the year 800. Or, if you assume 3 generations per 100 years, then 68,719,476,736 ancestors from the year 800. This makes the difference between Iceland and all of Europe look like a rounding error. Abductive (reasoning) 08:14, 23 June 2024 (UTC)

I think there are some flaws in your assumptions. ←Baseball Bugs ^{What's up, Doc?} carrots→ 02:04, 20 June 2024 (UTC)

In the more densely populated parts of Europe, there's a village every 2 km. Even centuries ago, people could easily marry someone from three villages away. Back in the 17th–18th century, your ancestors 6 generations back could come from a 5000 km² area (assuming no mass migrations, which did happen), housing around 200,000 people, more than the entire population of Iceland back then. (Rough numbers.)

You cannot assume Iceland is representative for Europe. PiusImpavidus (talk) 09:54, 20 June 2024 (UTC)

Of course you can, they are the same species, and mate the same way. Abductive (reasoning) 09:38, 21 June 2024 (UTC)

Are you saying that marriage customs in Iceland are identical to those throughout the rest of Europe? ←Baseball Bugs ^{What's up, Doc?} carrots→ 11:34, 21 June 2024 (UTC)

Then people in Iceland must conciously avoid mating somebody with a common great-great-great-grandparent. I don't know Icelanders that well, but here on the continent most people don't know who their great-great-grandparents were, even when it can be looked up in the archives. Else, random chance makes cosanguine marriages within 6 generations more likely on Iceland, simply due to the smaller pool to draw mates from. And if Icelanders conciously avoid cosanguine marriages within 6 generations, they may be less common than on the continent. PiusImpavidus (talk) 15:10, 21 June 2024 (UTC)

Yes, there were very explicit rules shared by everyone in the Catholic world and probably in all Christendom. You went to the priest, they looked in the church register and worked out the consanguinity using a mathematical method. If it violated the rule (mentioned in the article Libellus responsionum), you had to apply to the Pope in Rome for a dispensation, which he would use to extract a lot of money from the nobility, who were more likely to engage in close marriages. Abductive (reasoning) 07:58, 23 June 2024 (UTC)

Anyone who has studied their own family tree will probably know the answer for themselves, but even if that information could be compiled across all trees somehow, there's no assurance it would represent a reliable average. ←Baseball Bugs ^{What's up, Doc?} carrots→ 08:11, 19 June 2024 (UTC)

For Cleopatra VII I find 24 individuals, assuming that Cleopatra I had four different grandparents. In particular, Ptolemy VIII and Cleopatra III, themselves uncle and niece, where great-grandparents of Cleopatra VII along three different lines and great-great-grandparents of hers along two more lines. There may be Egyptian royals where you find an even lower number. Assuming the family trees are correct; amongst nobility extramarital sex happened sometimes on purpose to prevent inbreeding. PiusImpavidus (talk) 09:11, 19 June 2024 (UTC)

Then there's King Tut, whose parents were brother and sister. ←Baseball Bugs ^{What's up, Doc?} carrots→ 11:35, 19 June 2024 (UTC)

From a distant sociological point of view there is nothing like - exists akin without a fully homogeneously structured population. Except for one given durable period in insolated Iceland, and outrageously punctual, this or that other capital city blessed with the kind of magical aura making their burghers view themselves shiningly aristocratic. It's well known that otherwise, they'd finished dissolving in cretinism. --Askedonty (talk) 21:48, 22 June 2024 (UTC)

So how many different persons within the 7 consanguinities of King Tut? Also, how many different persons within the 7 consanguinities of Charles II of Spain (see Avunculate marriage#Medieval European royals, there are only 24 different persons within the 5 consanguinities of Charles II of Spain)? Also, how many different persons within the 7 consanguinities of Alfonso XII of Spain? Also, how many different persons within the 7 consanguinities of Ferdinand I of Austria? Also, how many different persons within the 7 consanguinities of Cleopatra VII (see Pedigree collapse)? Where for a “normal” person the answer is 127. 36.233.246.191 (talk) 08:29, 21 June 2024 (UTC)

King Tut: Eighteenth Dynasty of Egypt family tree is incomplete and some lines are uncertain, but other dan his parents, who were siblings, the next pair of ancestors who were related happened 8 generations before. I cannot conclude that the number as asked in the question is fewer than 63.

Charles II of Spain: 49. Going more generations back, there are more consanguinities to be found.

Cleopatra VII I already mentioned above: 24.

PiusImpavidus (talk) 16:20, 21 June 2024 (UTC)