Surnames and illegitimacy - is my math correct?

[melba_schmelba]

If the supposed average rate of illegitimacy is 5% - does that mean, in 10 generations i.e. on average, about 300 years, the likelihood of your ancestor in the male line being someone of a different surname is 50%? And in 600 years, it is almost certain that one of your male ancestors would have had a father who was not who he was meant to be (or they inherited their mother's surname) ?

[Kiltpin]

If the supposed average rate of illegitimacy is 5% - does that mean, in 10 generations i.e. on average, about 300 years, the likelihood of your ancestor in the male line being someone of a different surname is 50%? And in 600 years, it is almost certain that one of your male ancestors would have had a father who was not who he was meant to be (or they inherited their mother's surname) ?

 

I don't think so. Surely "average rate" implies across the generations. Regardless of the number of generations, the percentage remains the same. 

Regards 

Chas

[Joby86]

This post is so interesting, I am clueless with the most basic things but I never contemplated the rates of illegitimacy or anything else to do with the subject. My maternal grandmother was as far as I know born as an illegitimate child and trying to find out who her mother and father were but struggling. I hope you can find out what you desire

[melba_schmelba]

If the supposed average rate of illegitimacy is 5% - does that mean, in 10 generations i.e. on average, about 300 years, the likelihood of your ancestor in the male line being someone of a different surname is 50%? And in 600 years, it is almost certain that one of your male ancestors would have had a father who was not who he was meant to be (or they inherited their mother's surname) ?

 

I don't think so. Surely "average rate" implies across the generations. Regardless of the number of generations, the percentage remains the same. 

Regards 

Chas

Ah, but I am not talking about the probability of each event individually, I am talking about the accumulated probability over many generations that at least one ancestor in the male line will have been illegitimate .

[Joby86]

I'm no expert so don't quote me but I get the impression that the likelihood of ancestors having different surnames over the periods of time you gave as an example or over any time would be expected and I would think that illegitimacy doesn't really come into it in the respect of the illegitimacy rate and different surnames.

I may be wrong as I say but my maternal grandmother was born illegitimate and the amount of different surnames that have cropped up over a 300 year period are vast lol I think that possibly the illegitimacy rates have changed over the years for many reasons

[melba_schmelba]

This post is so interesting, I am clueless with the most basic things but I never contemplated the rates of illegitimacy or anything else to do with the subject. My maternal grandmother was as far as I know born as an illegitimate child and trying to find out who her mother and father were but struggling. I hope you can find out what you desire

Well, I wasn't really talking about a specific event of illegitimacy Joby (although I do have several instances in my tree) , I was just speculating really, considering we can now get Y-DNA tests (but also a basic Y-DNA result from 23andme or LivingDNA) and we can find out if we match other people of our surname, or might get a surprise and find we don't match people of our surname but lots of people of another (talking specifically of a FTDNA Y-DNA test that would give that ability). I know for example someone doing a surname study and has noticed that several branches have the same Y-DNA but some do not (but have no knowledge of any illegitimacy in their ancestry).

I may be wrong as I say but my maternal grandmother was born illegitimate and the amount of different surnames that have cropped up over a 300 year period are vast lol I think that possibly the illegitimacy rates have changed over the years for many reasons

I was meaning in the male line specifically  , in DNA terms that is only something men can test for  (a woman could get her brother/father/uncle to test to find out a Y-haplogroup associated with their father's male line). I am sure illegitimacy rates have varied, especially when lots of men died, i.e. in the World Wars, or if you had female ancestors who lived in a war zone - Genghis Khan and his soldiers left a traceable genetic imprint all the way to Eastern Europe I believe.

[Joby86]

If you don't mind me asking and it is purely out of genuine interest,... What exactly is it that you want to find out using the illegitimacy rate over a certain period to understand if the family surnames would differ? I just can't see how they can both be an avenue to go down or a method that may take you off track so to speak. Please don't think I am questioning you or anything impolite, I really am interested in this post as I love these kind of things

[melba_schmelba]

If you don't mind me asking and it is purely out of genuine interest,... What exactly is it that you want to find out using the illegitimacy rate over a certain period to understand if the family surnames would differ? I just can't see how they can both be an avenue to go down or a method that may take you off track so to speak. Please don't think I am questioning you or anything impolite, I really am interested in this post as I love these kind of things

Just curiosity Joby, not trying to trace anything specifically . Many people are quite attached to their surnames, but the truth may be that, after a certain amount of time, your ancestor in the male line being someone of a different surname will be quite likely. If you had a known illegitimacy in your recent male line, or you were a man who was adopted for example, in that case you might be particularly interested in getting a Y-DNA test, but the in depth tests can be expensive, i.e. FTDNA's most expensive test the Big Y-700 FTDNA is currently on sale at £290

https://www.familytreedna.com/products/y-dna

It would allow you to have in depth matching to others in the FTDNA database and you might be lucky to have an exact match, but often people don't. But there would be other things you could do, i.e. look at your 23andme matches to see if you could see a pattern in close matches in their Y-DNA.

[Joby86]

I feel I should confess that I have no idea whatsoever what you are on about reading the varying DNA tests you mentioned lol I have been trying to find out information about the birth mother of my maternal grandmother who was illegitimate and adopted aged two