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Comment by not_knuth | Hacker News Reader

I can't help but feel that some combination of the Birthday paradox [0] and primates churning out stories [1] is going on here.

[0] https://en.wikipedia.org/wiki/Birthday_problem [1] https://en.wikipedia.org/wiki/Infinite_monkey_theorem

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What accounts for the missing sister though? If the seventh sister was last visible 50000-100000 years ago, how the myths are trying to account for it now without the memory?

I think the idea of the 100,000 years of memory is plausible, but I think it's likely to persist because the number seven seems to be universally important to humans.

People could potentially have superimposed the number seven on the story, as per the rainbow's seven colours and Newton.

Since when is 7 important though? The species didn't have much of a math up until 5000-10000 years ago.

That is an interesting claim, the wikipedia articles about the history of math claim that the earliest written examples are from 3000 BCE. Finding a written record older is rather unlikely since that corresponds roughly to the oldest written texts in general. We do however have evidence of tally marks that date back to 35000 BCE[1] with one use possibly being a lunar calendar.

[1] https://en.wikipedia.org/wiki/Tally_marks

I'm going to go out on a limb here and claim that humans have been able to count since before you'd consider them human.

Lots of animals are able to count and it's ridiculous to assume that any individual with even a rudimentary language wouldn't be able to.

With which I mean to say that you don't need a formal understanding of 'mathematics' to count.

Further there's nothing mathematically super special about the number 7. You might say "it's a prime, and also X, Y, Z", but there's pretty much an infinite number of properties you could find for any number you choose.

There are, even today, languages that lack words for numbers higher than 2, 3, or 4 -- including a number of Australian languages. This tends to be more true for languages of contemporary hunter-gatherer. (See, e.g., Caleb Everett's Numbers and the Making of Us: Counting and the Course of Human Culture and references therein, or this article: https://theconversation.com/anumeric-people-what-happens-whe...). Studies of people who are native speakers of such languages actually do have difficulties keeping precise track of different numbers of items, at least at the level of five or more.

(There are Australian languages with more extensive number words, which is probably where the examples of "Pleiades = 7 women" stories come from.)

>Since when is 7 important though?

Since one moon phase takes that long.

7 is an important number across many cultures which pops up again and again. So is 8 (Eightfold path, 8 days of Hanukka, 8 Beatitudes, 8 Gates of Heaven). So is 6 (6-pointed Star of David, 6 Days of creation, 6 Articles of Belief, 6 Ministries, 666). So is 5. So is 9... There are many more things to be counted than there are numbers to count them with. Saying everyone decided on 7 stars because they just all liked the number 7 doesn't pass the sniff test.

Isn't this the strong law of small numbers? They're likely to be reused often because they're so small.

Perhaps there was a long time where people with slightly better eyesight could tell them apart while others couldn't, or when atmospheric conditions would obscure it. That might seed stories of the last sister being missing or coming and going.

We need numbers to calculate the likeliness of such scenario, but you just change the scale of the time from 100000 to let's say 30000 years.

Based on the analysis, it is very likely that the 7 stars were more distinctly visible but then gradually became harder and harder to see upto about 30-40k years ago. So cultures started making stories for why it disappeared. The fact that the stories of why the seventh sister disappeared seem different across cultures may possibly indicate the cultures had already separated when that happened.

Can you explain why this is related to the birthday paradox please? I don't get it, sorry! :)

When a million monkeys are typing stories, the odds of two of them being similar enough to be considered the same is _not just_ the odds of the millionth monkey creating a similar story.

Just like the odds of two people in a group having the same birthday is surprisingly low, so are the odds of different cultures coming up with the same story.

If you add a bit of selection bias, where you ignore all cultures that don't have a seven sisters story and ignore all the other myths that are not similar and you could end up with this unsurprising coincidence.

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