In inspiration from an other thread: If a person was born 2000 year ago

[Spirit of Light]

If a person was born 2000 years ago, how many relatives would it be possible living today by only this one person and a wife?

Let's say there are about 25-30 generations in 1000 years so it will be around 50-60 generations back from today to the year 2000, Right?

And let's say the family in the year 2000 get two kids, who again get 2-3 kids. who again all of them get 2-3 kids. Do you see where this going?

Would it even be possible to pinpoint ONE person in history back to 2000 especially if we do not have a body to take DNA of it?

In general, I know that it is possible to get an overview of where our heritage comes from far back, out from a DNA test taken today. But pinpoint one person?

My question, in the end, would we not all be related to many 1000 of people just a few generations back in time?

 

[Terry Sampson]

If a person was born 2000 years ago, how many relatives would it be possible living today by only this one person and a wife?

Ha! Melissa's claim hooked you, didn't it?

 

[exchemist]

If a person was born 2000 years ago, how many relatives would it be possible living today by only this one person and a wife?

Let's say there are about 25-30 generations in 1000 years so it will be around 50-60 generations back from today to the year 2000, Right?

And let's say the family in the year 2000 get two kids, who again get 2-3 kids. who again all of them get 2-3 kids. Do you see where this going?

Would it even be possible to pinpoint ONE person in history back to 2000 especially if we do not have a body to take DNA of it?

In general, I know that it is possible to get an overview of where our heritage comes from far back, out from a DNA test taken today. But pinpoint one person?

My question, in the end, would we not all be related to many 1000 of people just a few generations back in time?

It's a good point. 2 to the power of 50 is about 100 bn. So assuming 2 children every generation, one person could be the ancestor of more than the total population of the the Earth today.

In other words, every member of today's population could easily have some of the DNA of every living individual at the time of Christ. Of course they won't, since some lines of succession died out, some never got started and the population has not been perfectly mixed geographically, but it is not mathematically impossible at all.

Cool.

 

[Spirit of Light]

Ha! Melissa's claim hooked you, didn't it?

No I just wanted to see if others also could see this fault about one lineage

 

[beenherebeforeagain]

If I recall correctly, a better estimate is 40 to 50 generations per millennium (it's a shame there's so little standardization in definition...but as I recall the definitions from genealogy and demographics varied due to various assumptions and calculations. The shortest definition, iirc, is 22 years or thereabouts, while the longest is somewhat above 30 years. Remember, until the last century, most people died before the age of 35...

at two surviving children in each succeeding generation would 2^80, or 1.2x10^24 descendants in the current generation...three per generation would be 1.5^38...

Of course, if there was only one breeding child from each generation, the total in this generation would be 1 (because people live longer, there might be 3 living right now...)

...but in order for that to happen, the original DNA of the Jesus-Mary child would have been cut by half in each ensuing generation (as there would be no other Jesus-Mary lineage members to contribute their genes), so only 8.3x10^-25 would remain...

the only way to have more than that tiny fraction would be for there to have been considerable inbreeding...

 

[ChristineM]

If a person was born 2000 years ago, how many relatives would it be possible living today by only this one person and a wife?

Let's say there are about 25-30 generations in 1000 years so it will be around 50-60 generations back from today to the year 2000, Right?

And let's say the family in the year 2000 get two kids, who again get 2-3 kids. who again all of them get 2-3 kids. Do you see where this going?

Would it even be possible to pinpoint ONE person in history back to 2000 especially if we do not have a body to take DNA of it?

In general, I know that it is possible to get an overview of where our heritage comes from far back, out from a DNA test taken today. But pinpoint one person?

My question, in the end, would we not all be related to many 1000 of people just a few generations back in time?

Taking your OP specifically. Birth rates were far higher in the past but mortality rates were appalling. It would be a lucky family who managed to bring 1 in 10 children to maturity. Add in to that the wars and pestilence that devastated the adults of childbearing age you wind up with an almost static population growth for 1850 of those 2000 years.

However the descended from JC idea is somewhat way out there for many reasons, the DNA being just 1. Did he actually exist? If so did he father a child? Did that child survive?

Just a thought on JCs DNA if it exists, the Vatican or whoever has title would never let it be tested or even mapped, it could very well destroy a faith if the results showed his y-chromosome to be of Roman decent

 

[Polymath257]

the only way to have more than that tiny fraction would be for there to have been considerable inbreeding...

Bingo!

In most towns before fairly recently, the population seldom bred outside of the town. That means that within a few generations everyone in the town was related to everyone else in the town.

The exponential growth in numbers as you consider either descendants or ancestors doesn't extend back past about 10 generations. More than that and inbreeding plays a significant role in the numbers involved and the totals start to level off.

 

[Terry Sampson]

If I recall correctly, a better estimate is 40 to 50 generations per millennium

The "average number of years" per generation is an estimate. Currently,

The maximum number of ancestors that an individual can have in a generation that is a definite number of generations before him/her, assuming that there was no inbreeding [which a far stretch of the imagination] is calculated as follows: 2^n = x
where n is the number of generations back and x equals the number of individuals in that generation.

Assume you want to know how what the maximum possible ancestors is that you could have had 2000 years ago.
2000/30 = 66.6666667 rounded off to 67 generations before you. 2^n = 147,573,952,589,676,412,928 which is: One hundred and forty-seven quintillion five hundred and seventy-three quadrillion nine hundred and fifty-two trillion five hundred and eighty-nine billion six hundred and seventy-six million four hundred twelve thousand nine hundred and twenty-eight.

A rough rule, when talking about autosomal DNA which is the DNA that you inherit from your mother and father, is that, if there has been no inbreeding, given the mixing of different lines and propensity of a specific line's DNA to "fade" out down through generations, any individual's DNA will, at most contain a very, very small amount of their ancestors 7 generations before them. In fact, the amount of a 8th generation ancestor is so small that not even a somewhat-informed genetic genealogist would suggest that an autosomal DNA match could be used as evidence of anything other than evidence of a human may have been your ancestor.

Y-DNA and Mitochondrial DNA, however, are useful evidence when estimating a person's ancestral- paternal line or -maternal line ethnicity, because each is passed, in the first case, from father to son but never father to daughter, and in the second case, from mother to child (males and females) but never from father to child.