How many descendants does a pre-1700 ancestor have? 67,108,864

+25 votes
3.2k views

67,108,864.

This essay is especially addressed to new people to consider, before they rush to certify as pre-1700, because they mostly want to add that 1620s ancestor they have in their family member's research.

The point I wish to make here is that the chances are extremely HUGE that somebody has already created that profile, because there are a few living genealogists among those 67 million direct descendants.

Here is how the math works. Assume a typical generation is 25 years. From 1650 to 1980, there have been 13 generations.

I start with a presumption that each ancestor has four children. Of course it varies with time, some descendants have much more children, some have less or none. So four seems a reasonable presumptive average for each of them.

So the ancestor born 1625 has four children. Each of them has four children. That makes 16 grandchildren for the 1625 ancestor. In actuality, he has 20 descendants, 4 children + 16.grandchildren. But I am going to ignore that complication, just to be even more conservative. So the number I come up, with 67 million, is really just the number of living descendants today, and just in the 13th descendant generation, born 1980.

The way the math works to get there is 4 to the power of 13, which is 67,108,864. If you include those children's parents as well, born 1955, then add another 16,777,216 to that. That parent generation of descendants is 4 to the power of 12.

These days people don't have so many children as four each. But before the 20th century, they commonly had a dozen or more. So I think the 67 million is a reasonable, conservative guesstimate.

But even if you don't follow the precise math, or would nitpick it (easy to do, please feel free) please come away with an understanding of the key point I wish to make -- which is that when you are adding an ancestor in the 1600s, or especially earlier, you are presuming to personally take on the responsibility of ancestral identification for tens of millions of living and past people who are directly descended from that ancestor. So are you really prepared for that responsibility? Are you the only genealogist who has presumed to do so? And are you the best single one genealogist among them all, who is really prepared to accurately, or firstly, do so?

asked in The Tree House by Steven Mix G2G6 Mach 3 (36.5k points)
edited by Steven Mix
What a thought provoking post Steve. Thanks for sharing!!!
Thank you, Dorothy!

Because of endogamy the actual total number of descendants is almost invariably less than the theoretical number.

For example, Thomasine Frost (1560-1653) has been a topic of discussion here recently. She likely has more living descendants than the average person of her generation, but since I know I'm descended from her on several different lines, I'm very sure that the number of nonduplicated descendants is well below the theoretical number.

Oh, that is an interesting point, Ellen. By the math, you would be counted as a unique descendant child of hers, on one branch.

But in fact, you also appear mathematically as a descendant child of hers on another branch. So if that pattern repeats a lot, then a cohesive inter-generational community will form more of a replacement population, rather than an exponential growth population for each ancestor within the community.

And eventually for all people in the world, there will also form a great slowdown in the exponential growth of the number of any ancestors descendants, because eventually ancestors become shared.

So I think the numbers probably work well enough mathematically in the low to mid millions, but once the math gets into the billions of projected descendants, the math model will become a great over-statement, because more and more descendant individuals cease to be unique descendants on any given branch.
Excellent Steven.  Thank goodness there is tree collapse, as Ellen stated.  My husband has several 3 - times related ancestors in the 1700's  In other words, he is related to his great-X-grandfather/grandmother 3 times through different children of theirs.  He has about 4 of these grandparents (big families).  I only have 2 that I'm pretty sure about and I'm only related to them twice.  There may be some more on my mom's side, I just don't have it all worked out yet.  I'm sure there are more if you go back into the 1600's.
Thank you for your work.

Endogamy of various sorts create genealogical collapse, so not all unique descendants are produced in every line.  Some of the unique individuals born died out early, so they, in turn, have no descendants.  Some were married and never  had descendants.  On the average, you say if a couple in every generation that had four surviving children who married and had children and their children did the same, one couple might conceivably have X number of descendants.  

Obviously, when first cousins marry, etc., the number of unique descendants decrease as the same individual is counted on two or more different lines.  Second cousin marriages follow suit.  Double second cousin marriages collapses more lines and so on.  

I don't want to take away from your statistical research, but to be more accurate one has to take into account a number of other factors than just survival and reproduction.  Wars and epidemics have played a big part in reducing the number of children in every generation that survived and reproduced.  The actual number of descendants from the Mayflower pilgrims seem to be far less than the statistical number generated on the basis of 4 surviving children for each generation who in turn produced children who survived and produced children.  

Your statistical model is based on strict exogamy which almost never happens in newly immigrant communities.  There's always some endogamy as the available sexual mates in the gene pool are limited.  It's also true that some individuals have multiple spouses.

Excellent observation and eloquently put Steven, thanks! Here is one recent example of a high profile duplicate: https://www.wikitree.com/g2g/422326/how-was-this-duplicate-gedcom-made-possible I have mixed feelings about the following statement: "I have mixed feelings about your message. On the one hand, we don't want inexperienced people wrecking good established work, but if the profile is not there yet or has not been well developed, we want to encourage people (even if they don't think they are the foremost expert on the person) to take a first stab at it since the profile can always be improved later by others. You don't have to be the best, you just have to be willing to help and respectful of other's work. We currently have tons of profiles from the 1600s that are not well developed. What we need most is people willing to take the initiative and put in the effort to improve them. Discouraging people from working on a profile unless they think they are the world's foremost expert on the person is probably not what we want to do".

My observation is that yes - there are loads of pre-1700 profiles out there waiting to be addressed and sourced. What in my humble opinion is not needed is enthousiastic people with no or little experience to add or enter information [because the negative side to this is de-validation and the wrecking of established good and ongoing research]. There are millions more post-1700 to current date profiles (even my own) that need more urgent adressing. It is difficult enough to collate and research the pre-1700 (even pre-1800) profiles. I experience the strain that a project ca 1652 (and earlier because of the progenitor factor) to 1806 must endure to guide all the editing and adding and dis-connection and merging into a coherent and validated body of collaborative research. Yes - people do feel left out and it does hurt to see them wanting to help but not knowing how (the main reasons - the steep learning curve that WikiTree as; working with the Wiki markup languages; having to deal with all of the disruptive effect on the validation proces but very necessary at times changes in protocols, boilerplates, policy).

I am still of the opinion that a pre-1800 project and especially pre-1700 is not a sandbox for new WikiTreers to learn the ropes in. I for one am still correcting my own mistakes from when I started out at the end of 2013. I am also lucky in that I only collate the gedcom and manual fallout from others. I am thankful that I have never done a gedcom myself. By the grace of ...

While I fully agree that it's important to practice on 1800s profiles before going pre-1700, I would like to qualify the notion that "the chances are huge someone has already created your pre-1700 ancestor". It is probably the case for Americans, but there are areas in the world where it's theoretically possible (though again, NOT recommended unless you're experienced and really know what you're doing) to create pre-1700 profile upon profile in a complete desert. I am French and have a whopping 2 cousins on Wikitree, one who is no longer active !
That is a very valid point about international family, Isabelle. Even in early America, I am finding that, despite my math above, I can add a surprising number of unique profiles in the era from 1670 to 1700.

There are many profiles who are the later descendants that already exist, but the connecting profile below them and above the deeper ancestors is missing. So I find that I can connect quite a few lines with a bit of research and a few new profiles in that middle territory.

But it is when we get down a couple more generations, in the 1620s, where new profile duplication becomes a near certainty, for any ancestor who left descendants in America.

And then when people start to add profiles below the 1620s, and the matches don't exist, those new profiles are basically fantasy created from somebody somewhere along the way.

But generally, my warning of my essay is directed to brand new people, who are finding a big tree that somebody else made, and they are just copying deep ancestors. They have those ancestors in the source tree because they have been researched and copied and propagated already dozens, hundreds of times.

They don't have the truly missing ancestors, that are the difficult connecting links. So for the most part, they are just adding again what already exists, and has already been added dozens of times, in many cases.
I haven't read the analysis, but it's not true that most pre-1700 profiles have already been created. In my experience, less than 10% of the people I look for have profiles already. We haven't even come close to fully covering well attested pre-1700 genealogical sources like the English heralds visitations. Open an random visitation and check to see how many of those people are on wikitree. It's surprisingly few.
4 descendants per generation is a pretty high number. Even royalty doesn't usually go that high. It's usually between 2 and 3 and toward the lower end of that. It is, however, generally true that there's a time threshold before which any random person you pick who had progeny is almost certainly an ancestor. I think it usually works out to the late medieval period for England, and probably the Black Plague bottleneck makes it so that anyone who survived that and left descendants is an ancestor of virtually every person of English descent. There's a page here where the estimate is done for descendants of Edward III.
https://community.dur.ac.uk/a.r.millard/genealogy/EdwardIIIDescent.php
1. NO GEDCOMs

2. No Ancestry links as sources. Please. Leaves blowing in the wind. Hint.

3. Think pedigree collapse as significant factor as most people married

   someone within four miles of their home prior to 1850.   Whatever the number in the millions of living descendants, we can all agree that we should all do what we can to get it right.

Wikitree has made me a better genealogist.  Thank you.
I don't understand what the problem is with GEDCOMs?

I have added about 3000 people, and yes, they are not pre-1700 which may mean that I should not reply here, but there has been one (count it!) person who already had more than just that individual who was duplicated.

GEDCOM is not evil, and should not be vilified in such a blanket form!
GEDCOM is a tool. You called it evil. They are neither food or evil in my way od thinking. Tools are only useful as the skillset of the toolhandler. There are lengthy discourses here on wikitree about the mess that gets created by all the GEDCOM uploads. Irresponsible users upload and never ever go back to clean them up. To a large degree they duplicate references that are unsourced internet family trees.  There is a better standard now than earlier, but it involves dedicated wikitreers spending time reviewing the GEDCOM before allowing it to be added. I am not involved personally so there may be a point or two missed.  

Let me reiterate my position. GEDCOM files are more trouble than they are worth due to the lack of attention to source quality and clean up of something as simple as a personalized numbering system . They are loaded and many are never touched for years.

No GEDCOMs.

12 Answers

+22 votes
 
Best answer
One estimate for descendants of ALL the passengers of the Mayflower is 35,000,000. See discussion at https://www.wikitree.com/g2g/231659/35-million-descendants-from-the-mayflower-in-1620?show=231659#q231659 and I think that may be 4x to 10x too high, so 67,000,000 from one person is probably way too high. Also clearly a lot of variability in number of descendants from person in 1600 to another. Could be anywhere from 0, to a few, to millions.

I have mixed feelings about your message. On the one hand, we don't want inexperienced people wrecking good established work, but if the profile is not there yet or has not been well developed, we want to encourage people (even if they don't think they are the foremost expert on the person) to take a first stab at it since the profile can always be improved later by others. You don't have to be the best, you just have to be willing to help and respectful of other's work. We currently have tons of profiles from the 1600s that are not well developed. What we need most is people willing to take the initiative and put in the effort to improve them. Discouraging people from working on a profile unless they think they are the world's foremost expert on the person is probably not what we want to do .
answered by Chase Ashley G2G6 Pilot (106k points)
selected by Lynden Rodriguez
Points taken. But even if my *conservative* guesstimate is too high by a factor of 100, then a person adding a brand new 1620s profile is taking on the responsibility for 670,000 living descendants born in the 1980s generation.

That still seems to me to be a HUGE responsibility to presume to take on. In what other endeavor, or field of work, would anybody presume to speak for almost a million peers?

So I simply want people to ponder it a bit, before they add or alter the most ancient profiles, based merely on a tree that they found somewhere from somebody at some time.

"That still seems to me to be a HUGE responsibility to presume to take on. In what other endeavor, or field of work, would anybody presume to speak for almost a million peer?"

But that's the glory of a wiki. It's not a huge responsibility because if I mess up, the millions of others will fix it.

"So I simply want people to ponder it a bit, before they add or alter the most ancient profiles, based merely on a tree that they found somewhere from somebody at some time."

Now THAT I can totally agree with. Add quality to the tree, don't spam it with junk genealogy that you haven't researched.

Well, if only there were a million fixers, and a just a few data dumpers. :)

It is precisely because of my having spent endless hours fixing and merging, again and again, which has prompted me to write the essay. So if I can get people to pause, and to work a bit smarter, especially when they first join and immediately start to duplicate ancient ancestors who already exist, I will be happier.
Another interesting point about the Mayflower, is that, probably, if you are descended from one of them, you are descended from ALL of them who had children. That is because they lived in a cohesive community, and later generations intermarried. So they share descendants down the line.

So basically, if the conclusion is that *a* Mayflower passenger has 35 million descendants, then my 67 million figure is really not so far off the mark.

Of course, each generation that you add or subtract to the calculation, will multiply or divide the total by the average number of children per generation. So it greatly matters how many generations we are precisely talking about.

It also greatly matters how many average children in each generation goes into the calculation. For instance, I originally wanted to state five children. But I came up with a calculation of over a billion descendants! So clearly, that number five is way too high for an average family size, in American descent.
Interesting answer Steven. I don't seem to be decended from any of the Mayflower passengers. This confused me because every Magna Carta Surety Baron is one of my Great Grandfathers.  Also, Deacon Samuel Chapin, Edmund Rice, Protestant martyr William Tyndall's father, John Plantagenet-King John I of England, Queen Eleanor of Aquitaine, Elizabeth Woodville York, - are all my great grandparents. I am the great grand daughter of dozens of Puritans who came to New England during the Great Migration (1620-1640). Therefore I have been confused by my lack of ancestors on the Mayflower.  Your explanation that they were a closed group who intermarried, is a helpful explanation

Interesting discussion. It caused me to recognize that my small handful of Mayflower ancestors are exceptions to that generalization about Mayflower passengers forming a closed community. Specifically, my four Mayflower ancestors include three who would not have been strongly inclined to marry within the Mayflower passenger community:

  • Two children of passengers who didn't accompany their parents on the Mayflower, but emigrated several years later, after their parents were dead (having died during the first winter): Matthew Fuller and John Rogers "of Duxbury"
  • A man who traveled on the Mayflower when he was a teenager, not in the company of his parents, and who wasn't old enough to marry until after a number of other immigrants had arrived: Henry Samson

The fourth is Peter Browne. His first wife arrived on the Fortune in 1621, and was thus presumably was part of the Mayflower community, but when he married his second wife in 1630 there were plenty of non-Mayflower women to choose from, and my ancestry is traced (somewhat tentatively) to him and his second wife.

Interesting!

Christine, I can see that your Gateway Ancestor Edward Kemp arrived in the 1630s. I think what is going on is that the Mayflower was just one of many voyages which quickly populated the colony.

So your particular branches must have spread out, before they could interact much with the small handful of Mayflower passengers. That would make sense, if in the first decade or so 99% of the population consisted of other arrivals and descendants. I have some like that in my line.

As I understand it, the actual Mayflower families simply became swamped by the larger pool of new settlers. So the chance of any particular one of them marrying into a Mayflower family became relatively very small.

New Netherland, on the other hand, is a different story. It was only about 1/10 the size of the Puritans. So whereas Puritans were made up mostly of succeeding waves of new immigrants year after year, the New Netherland families were largely direct descendants of each other, who married into each other's lines again and again and again. So I am descended from a bunch of them, and repeatedly.
Yes Steven. Some examples would be Thomas Harvey b.1617 who arrived with his brother William Harvey in Plymouth Plantation 1636 and John Whittlesey a founder of Old Saybrook  who bypassed Massachusetts Colony totally and settled in Connecticut Colony.
Hi cousin!
I think it's fine if inexperienced people create profiles, as long as they're OK with seeing them corrected. The main problem with wikitree profiles is that once they're created, some people develop this sense that they must be correct just by virtue of being here, and they fight tooth and nail to keep you from "destroying" them, even if they're full of unsourced and often ridiculously unlikely claims.
+11 votes
I belong to an international organization where most of us descend from the same couple in 1600s.  Michel Andres and his wife Appollonia Krieger  https://www.wikitree.com/wiki/Andres-222   They had 12 children.  I descend from their daughter Christine.  Over 400 people in this organization descend from this couple who we call our Mythic Couple.  Not means that I have over 400 cousins who are into genealogy but when I entered him he was the first one entered...   Go figure!
answered by Laura Bozzay G2G6 Pilot (468k points)
Ah, so I think the difference there being that it is in ancient Germany, and then into France, as I quickly glance at your descendant tree.

The vast majority of genealogy and WikiTree in particular is dominated by the United States and its precursor ancestor immigrants. So perhaps my essay should be qualified to address American genealogists tracing their American roots.
Michel has descendants who were in Colonial America.  Big family dispersed literally around the globe...   I think at last count we covered about 5 to 6 languages in that group...  I agree that the farther you go back you can expect the tree to grow exponentially.
+11 votes
As already mentioned, your figure is rather on the high side.  In addition to the fact that family sizes in the last few decades has greatly decreased, at least in the Western world, even in the early days not every child lived to be married or was able to have children.  Now if you look at the number of children your ancestors had you might notice mostly large families but that's partly a statistical anomaly.  Say a random sampling of 5 families came up with 0, 0, 1, 4, 12.  That would be a little over 3.5 children per family, but if you asked the children how many children were in their family it would average out to over 9 since most of them were in the larger families.
answered by Dave Dardinger G2G6 Pilot (368k points)
Well, I did invite people to nitpick my math. :)

But I hope the larger point of the essay does not get lost, that the descendant populations of 1600s ancestors (not mortality infants) is extremely large. And so people should always use great caution and consider deeply, before adding any such ancestor as a new profile.

As far as the modern era, birth control as a major population limiter really only dates to the mid-1960s. Before that, my parents had four kids, their parents had four kids and six kids, their parents had 8, 8, 6, 6, more or less off the top of my head. And so that is all just within the 20th century.

Going back into the 19th century, I can see that pattern continue just like that, on every branch, just from we have researched and recorded.

But as you go farther back, branches get lost to any particular researcher. So we don't see the common 6 and 8 kids anymore. We just see the one particular ancestor sibling that we happen to be tracing our descent from. So the other siblings exists, and had children, but we just don't know yet who they are. Their descendants may know who they are, but they do not know that we are cousins through the common parents.

When you look at any particular descendant tree, the vast majority of genealogy lineages remain incomplete like this, because we just don't know yet the common deep ancestors among the many thousands of living descendants, once we go back a couple centuries. Each of us only knows which ancestors trace along the line to our own descent, for the most part, with maybe a sibling or two that have also been connected.
I see, on Wikitree, a LOT of profiles with only one child.  Then I find the will and see 12 children listed.

Remembering back to my history at Uni - the colonists had very large families until the population swelled, the number of children per family waned, the colonists pushed west and the family sizes boomed - and continued booming until the 1960's.
+11 votes
But it is VERY unevenly distributed.

I have about 300 pre-1700 profiles (of which about 30 are  pre-1500)

Less than 10 of them are "shared" with other WikeTree profiles.
answered by Janet Gunn G2G6 Mach 5 (59.6k points)
When you refer to sharing, you apparently are talking about sharing with other profile managers. That's not necessarily a good measure of the number of descendants. Many of us are not managers (nor even on the trusted list) of the profile of every ancestor who has a WikiTree profile.
I was responding to this statement, which implies that there is another WikiTree-user  descendant who can do a  better job. And that you should not create, or work on, pre-1700 profiles unless you are a "super-genealogist"

Your calculation seems to ignore several factors

1- typically  half of the children die before reaching reproductive age

2- typically not all of the children marry

3-Typically some of the married children have no children

Yes, these get balanced out by the one surviving child who has 12 children, but i still think you are overestimating

I don't remember the source, but I remember reading a study of British titles.  It took each title when it was originally granted, and tracked how many generations until it died out (no known male -line descendants of the original person).

The key number was 6 generations. I do not remember if that was the average number of generations before it died out, or if it was the median,  "50% died out by the 6th generation".

Obviously if you include female descendants, it will go further.  But still there are LOTS of lines that die out completely.
Janet, I calculated as low as 4 surviving and procreating kids each, to intentionally account for the three things you list. From what I see, 6-8 kids per family is rather typical, before the 1960s birth control, and certainly in the prior centuries.

So 4 surviving kids who each procreate is maybe a 40% mortality rate in each past generation, which seems reasonable to me.
I am looking at a table of annual US population growth. About 2% growth around the year 1900.

So take a village of 100 people. At 2% annual growth, over a generation of 25 years, the village will become 150 people, in simple math. They add 2 new people per year, over and above the deaths. So each year, the village has four births, and two deaths. The net result is two new people added to the population each year.

So take a typical family in the village, at that growth rate. A family of six. Two grandparents, two parents, two kids. After 25 years, they are a family of nine, a 50% growth, matching the average growth for the whole village. To get to nine, the two grandparents and one infant have died. But they also added four new children who lived to adulthood, and two new infants born to the older children. That math is 6 - 2 - 1 + 4 + 2 = 9.

So they have five children surviving to adulthood. In my scenario, it takes only four of those five to procreate in numbers of generating four surviving children each, to make 16 grandchildren. So, before marriage, one of those five adult children dies of disease or in war, and one other has only one surviving adult child of their own, who goes on to procreate, while the remaining three original children of the five have five survivor children each.

So in the process of this one generation, there are indeed 16 grandchildren of the original parents, just as my math guesstimate would predict. And all that is based in the actual population growth numbers, so ignoring the relatively minor effect of immigration, for simplicity.

At this 2% annual growth rate, the rule of 72 says that population will double every 36 years. So we have, very roughly, 10 population doublings since 1656 as follows:

1656 - 300,000 base number, more or less

1692 -  600,000

1728 - 1.2 million

1764 - 2.5 million

1800 - 5 million

1836 -10 million

1872 - 20 million

1908 - 41 million

1944 -82 million

1980 - 165 million

2016 - 330 million
This doesn't take into account any new arrivals in the area. IIRC there has been considerable immigration into the US during the last 200 years.
Yeah, I would say that's consistent with my experience. Before 1700, I occasionally hit a tree that someone else is working on, but mostly I'm off in the wilderness by myself, and that's even when I'm actively trying to hook up to lines other people have documented. Usually, I make links to other trees a high priority, but even then they don't happen all that often. There are a few deep trees that have been extensively covered in secondary sources (whether they're right or not is another story), and I've noticed a lot of people tend to follow those back and conclude that Wikitree has a pretty thorough coverage because that particular tree is covered well, but when you're doing original research, it's a different story.
+8 votes

Just a small example.   Daniel Doty, the GG grandson of Edward Doty, of the Mayflower is one of my ancestors. 

https://www.wikitree.com/wiki/Doty-757

I've decided to start tracing some of his descendants and so far, he as 12 children and 42 grandchildren and I have more to fill in. 

I know I won't be able to fill them all of his descendants in, nor will I try, but I can at least get a couple of generations in.   

 

answered by Craig Albrechtson G2G6 Mach 6 (64.5k points)
+12 votes
If any of us were really intimidated by the thought that we are accepting some sort of awesome responsibility by creating a profile for an ancestor with many descendants, we would certainly stop long before we got to the 1600s and millions of descendants.  Fact is, of 67M descendants (or whatever number), about 66.99M don't care.  Ther ones who do care are free to ignore or reject your work, or replicate it in their own way, or jump in and try to help you improve it.  Usually, it seems, they don't do any of those things, they just give you a little pat on the hind quarters and say "I'm glad somebody is doing this.  Keep up the good work."
answered by Dennis Barton G2G6 Pilot (238k points)
I can assure you that none of my profiles (pre or post 1500) come form a "tree that I got form someone".  They are all backed up with sources and references.  And where I have had to make assumptions (as to whether we are dealing with one person, or two people with the same name) I spell that out too.

One thing that may make a difference is that all of my ancestors are in Great Britain. I am my own "Immigrant ancestor".  It seems that a lot of the problems crop up with people who are trying to trace the British origins of early immigrants to North America.

That doesn't make me  super  genealogist, just a competent one.
And there are already restrictions to exclude the incompetent from editing pre 1700 profiles.  Most of the really bad ones were created before we had the pre-1700 and pre-1500 certifications.
With you tracing lineage in Britain, Janet, I can see where the lineage might not have yet been entered. But as for sources, what sources are good enough for pre-1500? A lot of lineages have been replicated because people followed a source that has been discredited as complete fiction. That sort of thing is rampant in pre-1500, because some person once paid money to somebody to *find* the connections they wanted to have.

Do you have the original parchment documents? Can you decipher the ancient handwriting? Is there little damage from water, and sunlight fading, and insects, not so severe that some quality data transcription can truly be made from what still exists on the parchment? Are you experienced in interpreting the convoluted sentence structure that commonly existed in documents centuries ago? Are the variable phonetic spellings on the document close enough to modern words that the meaning of each phrase is really clear?

So the farther removed you are in expertise from each of those conditions, the more that possible errors are introduced, sometimes from wishful thinking. I know of one such document, or summary of such a document, in my lineage. And interpreting the thing is almost impossible to my eyes. I *think* I have figured out what it says. But I am not clear enough about it to publicly create the ancestors. And that only goes as deep as the 1400s.

So in dealing in this ancient era, when people say they have *sources*, what they actually have is a third-hand interpretation of something that somebody had once transcribed, and maybe amended, re-interpreted, maybe lost the trail of who did what with the info along the way. Unless your source is a professional genealogy journal item by a pro who has actually examined the original document and with the competence to read it properly.

Well, Dennis, the thing that prompted me to write the essay is because a new member created a duplicate 1650s profile, among several, and I set a merge pending.

Then the same person a few days later, added and atttached new duplicate parents to that pending merge profile. I mean, the merge pending was already linked right there. But the person failed to even look at the comparison, and see that original parents were already attached.

Keep in mind that this person had to pass the pre-1700 test in order to do all these inexplicable actions, after passing. And this sort of thing is not unique. It happens often. Even with identical spellings.

So my essay is a meager attempt to try to educate, to innoculate against such actions, maybe with a bit of shock value to get noticed.

But my personal wish is to enforce a universal moratorium against any pre-1700 profile for new members. Make them wait a month or three, no exceptions. That would at least give them time to poke around in the ancient profiles a bit first, to actually see what is already there. But I get resistance every time I suggest such a thing. So my essay is a different approach for me to try to solve this problem.

Most of my early sources come from HoP (History of Parliament) and VCH (Victoria County History), the authors of which ARE experts in interpreting early documents.

The other major source (which I have in transcription), the Tropenell Cartulary, attempts to discredit my ancestors to justify Tropenell's underhanded means of acquiring their lands.  No sugar coating there. Maybe because I studied (briefly, not my major) Old and Middle English in college, I do not have much difficulty interpreting it.  The bigger problem is interpreting the  internal inconsistencies.

Where the records exist, I actually find the 15th century genealogy easier/ more certain than the 18th century genealogy.

I am quite comfortable with your suggestion of a restriction for NEW members (with exceptions where appropriate)  But not for longer term members.
I too am extremely suspicious of any NEW pre 1600 profiles. I only trust existing proven pedigrees. Realistically, the chances of discovering some new unknown church document, land deed, Will, etc. - which uncovers the existance of new undiscovered ancestors - is so unlikely as unlikely as finding a newly discovered Hampton Court letter chest at a village antique shop. I consider it impossible.  Existing pre 1600 documents which have been saved and protected, have already been analyzed, and analyzed by experts in Middle English language style, law, ietc. My approach to my genealogy efforts is to trace my New World 20th, 19th, 18th, 17th century ancestors back to their "gateway" ancestor. Once I have linked in to a proven accepted Pedigree, i consider my work done. It would be presumptuous of me to dabble with and change Renaissance and Medieval pedigrees. I don't have the primary documents and i certainly don't have the expertise. I feel that it's important to maintain  humility on Wikitree and recognize one's limitations.
I think with more and more European cities / towns putting their histories and records on line we are finding access for the armchair genealogists to records from the 1600s that were not readily available before.  

I find this particularly true in France and German records today.  Most of those were not in either Ancestry or Family Search (might have been on microfilm in Family Search but had not made it online).  I have copious examples of this in my possession.  

France is actively working to get all records on line.  You have to be able to read French and Latin to make sense out of them but they are there.

Baden is doing the same in Germany.  I think Westphalia just did the same.
Christine may be correct when referring to British "sources", but my experience with Dutch pre-1600 sources follows Laura's comments. The Dutch digitalized their records after WWII, with most of them transcribed in modern Dutch. Both versions are easily available, as well as the original document, nearly always free of charge. Are these NEW?  To the archivist no, to me yes. The armchair genealogists, including me normally computer search birth, wedding, death documents by last name. Dutch pre-1600 sources are largely notarial and court documents, and require much more time to search. I extended my tree from 1590 back to a document of sale dated 1358 of a Jan van Weert and his wife Mette Jacobsdaughter selling a parcel of land to a nearby monastry (which kept the document all these years). I have not added these people to WikiTree.  Should I?
Gus I have pre-1700 and pre-1500 certification and have added many but not all of the people in my lines who fit these time periods.  I do try to find multiple sources.  Part of the problem is I may have a document that shows 3 people all sharing the same name... because these documents are for guilds and not genealogical they do not indicate relationships unless you luck into one that says so and so is the son of such and such.  We know they are all related because to be in the guild you had marry within the guild and these were very closely held family secrets.  We just don't always know if they are brothers, cousins, uncle and nephew, grandfather, son, grandchild.  What makes it worse is they may all have the same name.  So a lot of genealogy for this time period is guessing based on other known pieces of data like  (I am going to append a number 1, 2, 3 so you can follow this)  Jean 1 died in 1645 now we can guess he was likely born before 1625 if he was working as a master glass maker because that title typically took a minimum of 15 years.  Kids as young as 10 began journeyman status so the latest he would have been born was 1625 but it could be earlier.   Jean 2 took over the running of the glassworks in 1645 when Jean 1 died.  OK,  is he a master glass maker.. if so then it pushes his birth to 1625 too.. so are these brothers with names like Jean Paul and Jean Nicholas but the family call names of Paul and Nicholas did not make it onto the official document or is this father and son so it would then push the birth of Jean 1 back another 20 years or so?  Jean 3 has a birth record that shows a Jean (is it 1 or 2) as a father and a witness listed as a grandfather also listed as Jean.  So we now assume but have to explain the assumption here that Jean 1 is the father of Jean 2 and the grandfather of Jean 3.
Three cheers to the Dutch for dititizing their records. After reading some responses to my previous comment, I see that I have much to learn about ways to find new "old" ancestors.
As to old documents, handwritten originals, I've looked at lots of microfilms of them. These are all pre-1650, going back to 1400. Mostly land transactions.  Luckily all are in Latin, not Scots Gaelic! There are books, readily available in our library (admittedly the second largest University one in the world), which carefully describe the legal language of those days and also the "secretarial script" used, a sort of shorthand. I do, however, remember my middle and high school Caesar's Latin, which helps with the endings and grammar, which remain more or less the same to this day.

It wasn't really hard actually, to do the job. I did manage to prove the connection implied, but only implied, in a grant of (Scottish) arms to an 18th century cousin of mine. This line is Magna Carta project certified on Wikitree.

But this really isn't the point of Wikitree. Its NOT about original research, especially in that time period. The place to discuss that remains the old Usenet group soc.genealogy.medieval. Wikitree is about entering reasonably solid connections of existing lines.
+8 votes
I have a different method, that generates an actual, not theoretical result.  I am the admin of the Clan Donald USA DNA Project.

The "Clan Founder" (which he sort of was) was named Somerled.  He died in the year 1164. We are tracing his PURE MALE LINE descendants, i.e., bearing his Y chromosome. He had no surname, the surname starting more or less with his great grandsons. But paper trails say that the great radiation of the surname McDonald began with his 3rd great grandson who was named John, born before 1324 d.1387. We have paper trails of superb quality and matching DNA from three of his sons.

In our project we have about 900 men named M(a)cDonald or McDaniel (the southern US form, from the Gaelic pronunciation as heard by the boat-dock registrars.)  182 of them are male line descendants of John, as proven by the very unique DNA. That's 20%.

I surveyed online statistics from Scotland, England, Ireland, Canada, the USA, Australia, and South Africa. I estimate that there are 230,000 men with matching surnames there.   That works out to about 46,000 pure male line descendants of one man, living in 1350. Its actually more as there are some named MacDowell and the occasional adopted name.

Then of course you have to try to extrapolate to the descendants not in the pure male line.
answered by James McDonald G2G5 (5.2k points)
edited by James McDonald
My first cousin on my mother's side is married to a McDonald male (South Africa) ...
+6 votes

You make a good point - that someone alive in 1700 would have a lot of descendants alive today - but your numbers are massively out. This is for all the reasons given above - in particular both endogamy which reduces the numbers but also the number of 4 children per person is inaccurate and I don't think 25 years per generation is accurate.

For the average number of children, you can work this out relatively easily by looking at the population of the country in question and the natural increase (ie excluding migration) with time. I suspect the number will be much less than 4 - depending on the country I would expect less than 3.

Regarding the time per generation, most people started having children about age 25 but then continued for 10-20 years. I find using three generations per century more accurate for my family.

Given that you have answered your question both in the title ("How many descendants does a pre-1700 ancestor have? 67,108,864") and in your description, could I ask you to amend these to reflect these challenges?

answered by Andrew Turvey G2G6 Mach 2 (20.6k points)
Andrew, in the example above, I showed that the growth rate of the American population has been historically 2% per year. That number came from an actual statistical source chart, and accounts for annual growth after both birth and deaths, with a relatively minor effect from immigration.

I showed how the rule of 72 means that the population doubles every 36 years at that 2% rate.

I also showed how a village of 100 then becomes a village of 150 in a quarter century. Or a family of 6 in the village becomes a family of 9 in that time. The number of 4 children having 4 children still seems fairly accurate to me.

But I will concede that the total number of descendants is coming out too high by the naked math. And I think it is mostly a factor of the number of generations in the calculation. Endogamy may happen a lot in early generations, which will reduce the number of generations in the math. And that is where the big reduction happens.

Also what actually happens is that the exponential effect is not smooth, over a long time. it will randomly get interrupted on each of the branches along the way, and then have to restart the exponential growth from a lower than expected base.

So, for example, if say endogamy reduces the effective number of generations to 12 instead of 13, the total count is reduced by 4, to 16 million.

I don't think I want to alter the premise, because I want to show how the math works. And the actual final number is not quite so important, whether it is tens of millions or tens of thousands .The point of the essay is simply to encourage people to pause and think about the ramifications of the exponential descendancy, before they create that 1620s profile.

In other words, it is not just another profile that they are adding. It is rather the root ancestor of another tens of thousands or of tens of millions of more descendants.
I would guess that a LARGE contributor to the _US_  growth of 2% per year is immigration rather than reproduction.

Checking back my own ancestry I find my Great grandparents where born ~100 years before me (all I have definite DOB for are within 10 years of that), so 3 generations /100 years does seem more reliable.

The 4 children pre generation also looks like an exaggerated figure. AFAIK none of my great grandparents had more than 12 grand children. It seems that 3 children per generation getting married is closer to the truth among the data I have available, even with some ancestors marrying at least 3 times. In several places ancestors from the 1800's have only 1 or 2 known grand children despite their large number of children.

Using more realistic values of 33 years per generation & 3 children pre generation your calculation gives 310 which is 59049. Still quite a sizeable figure but WAY down on the 67 million estimate.

+5 votes

Pedigree collapse

https://en.wikipedia.org/wiki/Pedigree_collapse

"Without pedigree collapse, a person's ancestor tree is a binary tree, formed by the person, the parents (2), the grandparents (4), great-grandparents (8), and so on. However, the number of individuals in such a tree grows exponentially and will eventually become impossibly high. For example, a single individual alive today would, over 30 generations going back to the High Middle Ages, have 2 30 {\displaystyle 2^{30}} 2^{{30}} or roughly a billion ancestors, more than the total world population at the time.[2]

This apparent paradox is explained by shared ancestors, referred to as pedigree collapse. Instead of consisting of all different individuals, a tree may have multiple places occupied by a single individual. This typically happens when the parents of an ancestor are related to each other (sometimes unbeknownst to themselves).[3][4] For example, the offspring of two first cousins has at most only six great-grandparents instead of the normal eight. This reduction in the number of ancestors is pedigree collapse. It collapses the ancestor tree into a directed acyclic graph.".

answered by
+4 votes
The Wall Street Journal had an article not long ago by a Statistician saying if each generation had two kids and mother/father, when you reach 133 generations, you will have ONE TRILLION ancestors.

He didnt think that most families had 6-12 kids (no birth control).
answered by Christopher StJohn G2G2 (2.7k points)
0 votes

There is a mathematical point I want to make that I didn't see in the prior "nit-picking".  People have mentioned that some of the children will not live to reproduce.  The "zeroing" of a population can actually occur after several generations, and I think this is more common than many would expect.

In mathematical terms, you have given in your post an "exponential model" for the growth of a population, say, the descendants of John Smith born 1650.  The descendants of John Smith are a value that changes over time, and you could "model" it with all sorts of models.  The exponential model is wonderful because a mechanism explains how it arises (i.e., your explanation of how to arrive at 4^13 after 13 generations) and it is very simple, so easy to work with.  But any work like this is creating only a model of the world, not describing the world for certain.  It is a mathematical abstraction of what will happen, and while the real world is certain to differ from what your model says, you try to pick a model that will most closely describe what happens in the real world.  People have already explained how endogamy makes this model unrealistic after enough generations.

One of the most common ingredients to include that complicates the exponential model but also makes it more realistic is an "extinction threshold".  This is a threshold where if the population is low enough, and things go wrong, the population goes to zero. There would be some work to implement this (you'd need to move to a stochastic model, blah, blah, ... don't worry about that), but the point is, the long-term behavior of a population will end up doing two drastically different things:  growing or heading to 0 and then staying put.  It may take many generations to reach 0, but once it gets there, it is certain never, ever to grow.

My point is that the process of going to 0 can take more generations than one would expect.  I offer as an example Susan Jackson

https://www.wikitree.com/wiki/Jackson-27869

Susan was probably born around 1800.  She was one of six illegitimate children of James Jackson of Ballybay, a scion of a fabulously wealthy family from County Monaghan in Ireland in the 1700s.  They were politically active, and most of the family fled in the late 1790s and early 1800s.  

I am descended from Nothern Irish Jacksons, and a fourth cousin on my line found a letter written to her aunt from a woman named Lillian Virginia Koller in the early 1900s and sent it to me.  It was clear that it contained a transcription of the family bible of James Jackson of Ballybay, so I was very excited. No one seems to know this bible existed, or at least existed within memory.

With some help, I eventually traced Lillian's ancestry back to Susan.  Then I went looking for living descendants of Susan hoping to find one who may know about the bible, and so far as I can tell, there may be none, with the last descendants passing away around 1950.  You can see that she had quite a few descendants:

https://www.wikitree.com/genealogy/Jackson-Descendants-27869

(Actually, I didn't create profiles for them all because it got got depressing creating so many profiles for terminal lines.)

I have written to the Staten Island Historical Society Museum to see if the bible ended up in their collections.  They said that it is common for the last known scion of a house to pass away with a bible and that if no other relatives can be found, it may be bought at auction by a museum or historical society.

P.S.  I have done a lot of work on identifying people in the 1774 Rhode Island Census, which quite often includes going back and looking for ancestors into the 1600s.  There are many such New England profiles that do not exist yet on Wikitree.

answered by Barry Smith G2G6 Mach 3 (34.4k points)
+1 vote
I would like to offer a possible solution where uncertified and newbies can "practice" but do no harm.   What if we have a free space page where new pre-1700 profile data is entered (not into a form like a real profile but following the basic informational structure). Then badged folks and project folks like French Roots, German Roots, etc.  get to look at it and discuss it in G2G before it is actually added to the tree.   Things like spurious sources can be discussed, conflicted information can be researched and debated.  This would give everyone who has a vested interest a chance to review, collaborate, and refine before someone is actually added to the tree.   And if someone is not ready for prime time they still exist for reference in the free space page.   

What do you think?
answered by Laura Bozzay G2G6 Pilot (468k points)

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