You (maybe?) have thousands of ancestors from the 1600s
kayce.basqu.es
kayce.basqu.es
For example, my wife and I recently discovered that we're sixth cousins. This means that when our kids trace back their ancestry, there's an entire subtree on my side that is duplicated on her side, which dramatically shrinks the number of ancestors down from the theoretical maximum. And this is far from an uncommon occurrence—we most likely have many other subtrees in common that we simply don't know about.
> With fully random matings the number of your ancestors doubles every generation.
Edit: Just saw your other comment here. The answer seems to be more along the lines of "impossible to put a number behind": https://news.ycombinator.com/item?id=37387655
People whose families have been in one place for generations are much more likely to have a smaller set of ancestors than people whose families migrated many times over the last few centuries. And any given person's family tree is likely to have some subtrees that were sedentary and others that migrated, further complicating any attempt at an abstract calculation.
When the population is roughly 2^2n, you expect to lose one ancestor in that generation.
For the majority of the past four thousand years, almost everyone lived in farming villages that had ~50-100 families living in them, and mostly married inside those communities. Even just going to a neighboring village for a bride was something that only happened occasionally, but even when that happened, it was almost always the same few neighboring villages. This means that when you trace ancestry backwards, you always end up related to everyone living in a few villages, and then every few generations this extends to a new village. Then if you are related to a successful trader or soldier or something, it will suddenly double the amount of ancestors in a generation, but I really need to stress that this is rare.
The introduction of the bicycle did a lot for reducing inbreeding in farming communities, because it was something that a normal people could own, and allowed day visits to neighboring communities. Before that, it was entirely ordinary to live and die without ever traveling more than 10 miles from the place where you were born.
My wife and I are related through the same grandparents.
These are weird, but it makes sense - we're from smaller towns, which were settled not that long ago in the grand scheme of things. If you trace enough of us back, we're all probably related.
But the seriously trippy part is - my younger sibling and their spouse are related through the same great(x4 or so) grandparents. The sibling is from a different country that isn't even close to where we're from. Like literally the other side of the planet.
It blew my mind.
My son's mother's ancestry is very different from mine.
If anything I think we might live in period of the greatest number of long distance gene flow events in history. And I think this has been true for hundreds of years at this point.
EDIT: That's not to say inbreeding doesn't hugely reduce your number of ancestors, just that the modern world for many social groups has much less inbreeding than earlier societies.
So cool, I never thought about a generation limit to meaningful genetic contribution.
[1] https://en.wikipedia.org/wiki/Y-chromosomal_Adam [2] https://en.wikipedia.org/wiki/Mitochondrial_Eve
PS: see also references fromthe linked wikipedia pages
From the Wikipedia article:
> Although the informal name "Y-chromosomal Adam" is a reference to the biblical Adam, this should not be misconstrued as implying that the bearer of the chromosome was the only human male alive during his time.[7] His other male contemporaries may also have descendants alive today, but not, by definition, through solely patrilineal descent; in other words, none of them have an unbroken male line of descendants (son's son's son's … son) connecting them to currently living people.
(Reading the Eve article left me with even more questions than answers, but I'm still getting the sense that Adam and Eve are orthogonal to the "number of ancestors in 1600" topic.)
> fathers consistently older (30.7 years) than mothers (23.2 years)
https://projecteuclid.org/journals/notre-dame-journal-of-for...
> This paper is the third and final one in a sequence of three. All three papers emphasize that a proposition can be justified by an infinite regress, on condition that epistemic justification is interpreted probabilistically. The first two papers showed this for one-dimensional chains and for one-dimensional loops of propositions, each proposition being justified probabilistically by its precursor. In the present paper we consider the more complicated case of two-dimensional nets, where each "child" proposition is probabilistically justified by two "parent" propositions. Surprisingly, it turns out that probabilistic justification in two dimensions takes on the form of Mandelbrot's iteration. Like so many patterns in nature, probabilistic reasoning might in the end be fractal in character.
I believe it also has a feature somewhere for determining how closely related you are to someone. My wife and I discovered we are 13th cousins (or so).
And it has a really broad wiki to help you do accurate genealogy, with many country-specific tips and other pointers to other resources.
It will not disclose info on living persons, in the tree, except to that person (and maybe their children? I forget).
Lately I have not been active on the site and get less than one email per month from them, I think.
Biologists define the "identical ancestor point" to be the most recent time X in the past such that every person alive at time X is either an ancestor of everyone alive today, or of no-one alive today. Computer simulations suggest that the identical ancestor point is quite recent in geological terms, e.g., it's probably within the past few thousand years (it would be even more recent if we ignored remote places like Tanzania). See: Rohde et al (2004), "Modelling the recent common ancestry of all living humans", Nature. https://www.math.arizona.edu/~bhallmark/TMRCA/naturerohde.pd...
From the linked paper:
> In the case of Tasmania, which may have been completely isolated from mainland Australia between the flooding of the Bass Strait, 9,000–12,000 years ago, and the European colonization of the island, starting in 1803 (ref. 13), the IA date for all living humans must fall before the start of isolation. However, the MRCA date would be unaffected, because today there are no remaining native Tasmanians without some European or mainland Australian ancestry.
Oddly, portions of mainland Australia may have been as genetically isolated from each other as Tasmania, once particular environments were settled (ocean, river, desert, etc) they appear to have remained stable.
https://en.wikipedia.org/wiki/Truganini
day the Pintupi Nine entered the modern world https://www.bbc.com/news/magazine-30500591
Aboriginal mitogenomes reveal 50,000 years of regionalism in Australia https://www.nature.com/articles/nature21416
Each one of those people had a name (and a life, and thousands of ancestors themselves).
How many names of these 32,000 do you know?
While for many of my lines, I know the names to the 1600s and further.
Other lines dead end in the mid-1800s…what stories am I missing because of these all these dead ends?
Enough to bore my family! Genealogy is fun, at least for me...
With modern technology, it's easier than ever to dig into the primary sources and find out more about your ancestors.
But I would warn everyone to stay away from the big commercial genealogy companies. For one, they have extremely bad privacy practices (they will never, ever, stop spamming you), for the other, they have no interest in the truth and will happily tell you what you want to hear to keep you as a customer (they encourage very bad genealogical practices).
I use them for pointers to resources.
Archive.org is my primary research tool.
That is, assuming the officially recorded parents are the actual biological parents. It's not nice to talk about in polite society, but sometimes people are mistaken about biological parenthood, most often fatherhood but sometimes motherhood too (think: babies swapped at the hospital). All it takes is one error to invalidate the whole line behind it (though, eventually the line will hit your ancestors again anyway).
That's incomplete. It should be go back far enough and everyone is either your ancestor or is nobody's ancestor.
If your nearest common ancestor is a great-great-great-great-grandparent, that's not incest (it would most likely not even be known at the time of marriage), but it still leads to large amounts of duplication in your family tree. Every family tree will have many instances of nth-cousin marriages simply because people tend to marry people who live close to them.
It's very hard to calculate what the actual number would be because it depends a lot on where your ancestors lived and how much they migrated over time.
That really depends what you're imagining when you say "incest". In literal terms, yes, we're talking about mating between two people who share common ancestors. Those do not need to be particularly recent.
In genetics there is the concept of the "coefficient of inbreeding" which tracks how much of an individual's genome is identical-by-descent across both chromosomes. (That is, if you inherit a particular stretch of DNA from your mother, and you inherit the same stretch of DNA from your father, and the reason they are the same is that your father and your mother both inherited that DNA from the same person, then that stretch of DNA contributes to your coefficient of inbreeding.)
If you're imagining brother-sister marriages, that is a much higher level of inbreeding than would be common in human history. (Expected coefficient of inbreeding in the offspring: 25% assuming zero inbreeding in the parents, perhaps because they are themselves the offspring of a cross between an African Pygmy and an Australian Aborigine.)
But it is true that different populations have more or less inbreeding than others; we can say that Arabs tend to be more inbred than the French. This is not necessarily because they tolerate incest at closer degrees of kinship than the French. It is mostly because they have a greater quantity of still-relatively-remote incest. (Not the greatest example; Western Europe hugely stigmatized cousin marriage under the influence of the Catholic Church, so in reality Arabs do tolerate closer degrees of kinship in a marriage than the French do. But the concept is sound - inbreeding will "build up" in a population over time.)
You can't. The population of the world gets smaller as you go back in time.
There are that many open spots in your family tree, but, as you go back in time, you will see that each person in the tree simultaneously fills a large number of different spots.
A related but not identical observation: the set of all your ancestors is roughly 1/3 male and 2/3 female, despite the fact that there are an equal number of male and female spots in your genealogy. Males are doing more double duty than females.
As in one man getting multiple women pregnant?
The estimate I'm familiar with also says that historically about 80% of women, compared to 40% of men, successfully reproduce.
It's why evolution is such a no brainer. Think of a creature with just a few years of life. They have countless ancestors every century, every millenia. Countless millions and billions of parents came before us.
TLDR all Europeans may have a common ancestor as late as 1400 BCE, maybe 55 CE.
* https://www.scientificamerican.com/article/humans-are-all-mo...
* https://www.nationalgeographic.com/science/article/charlemag...
And no they did not teach me that in school ;D