moore2moore
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The following was posted on another thread, where it was slightly off topic, so I am relocating it here:
The following exercise will help people conceptualize which ancient DNA patrilines and matrilines survived into the modern era:
We all know that Italy is in the center of the Mediterranean, and that it was the "superhighway" during Greco-Roman times. It has been invaded by countless peoples: Neandertals, Cro-Magnons, Hunter Gatherers, Farmers, Herders, Samnites, Romans, Greeks, Goths, Franks, Lombards, Byzantines, Saracens -- to name some. We are all pretty familiar with the list.
Italy has the largest Y-haplogroup diversity in all of Europe. It is a land that has been coveted for millennia. I have seen this concept posted on other threads here, and I don't think anyone doubts it.
On the opposite extreme, Ireland has very low Y-haplogroup diversity. It is almost 80% one haplogroup.
Ireland is a land that has been ignored for millennia. The Romans said "no thanks." The Anglo-Saxons said, "no thanks."
There has not been much incursion into Ireland. (Note that I didn't say none). The fact that Ireland is an island, and westernmost, and cold, all help its isolation. I think most of us well know Ireland's geography and history.
If you populate one land, and every 200 years, 10% of the the population is new, you will end up with 10 different haplogroups after 2000 years. The ones that have been there longer will decrease in numbers. I think we all can grasp this mathematical concept.
If you populate another land initially, but there are no major introgressions to speak of after the first major settlement, then you will end up with FEWER haplogroups after 2000 years.
You see, over time, some males have only daughters. Some die before childbearing age because a bear eats them. Etc.
Those lineages die with them.
Put another way: If 10 people decide to populate a small island somewhere, and there are no further invasions, the number of lineages on that island can only go in one direction. It can't go up, barring a freak series of mutations. It can only go down.
The variability will decrease over time. This can (and judging by many posts here - DOES) give the ILLUSION that the original population was smaller than it was.
I repeat: a place that did not have widespread invasions will see the number of its patrilines and matrilines go in one direction only: down. This is true for all isolated places around the globe. If we let a place stay like that until infinity, eventually all people would have the same patriline and matriline, because a certain percentage die out every generation.
Note this is different from saying they will all be related. They can keep genetic variability to some extent, but patrilines are a binary equation: each generation, they die or have male offspring.
A locale having a large percentage of one patrilines can deceive people to thinking that that only one group of guys was having kids, because they were "royalty" or had "harems."
There is no place on the globe, not even in the case of Genghis Khan, where one royal line, family, or clan has direct offspring in the present that total more than 10% in certain regions.
This is scientific and mathematical fact. I don't know how more plainly to state it. Please let me know if anything is unclear.
The following exercise will help people conceptualize which ancient DNA patrilines and matrilines survived into the modern era:
We all know that Italy is in the center of the Mediterranean, and that it was the "superhighway" during Greco-Roman times. It has been invaded by countless peoples: Neandertals, Cro-Magnons, Hunter Gatherers, Farmers, Herders, Samnites, Romans, Greeks, Goths, Franks, Lombards, Byzantines, Saracens -- to name some. We are all pretty familiar with the list.
Italy has the largest Y-haplogroup diversity in all of Europe. It is a land that has been coveted for millennia. I have seen this concept posted on other threads here, and I don't think anyone doubts it.
On the opposite extreme, Ireland has very low Y-haplogroup diversity. It is almost 80% one haplogroup.
Ireland is a land that has been ignored for millennia. The Romans said "no thanks." The Anglo-Saxons said, "no thanks."
There has not been much incursion into Ireland. (Note that I didn't say none). The fact that Ireland is an island, and westernmost, and cold, all help its isolation. I think most of us well know Ireland's geography and history.
If you populate one land, and every 200 years, 10% of the the population is new, you will end up with 10 different haplogroups after 2000 years. The ones that have been there longer will decrease in numbers. I think we all can grasp this mathematical concept.
If you populate another land initially, but there are no major introgressions to speak of after the first major settlement, then you will end up with FEWER haplogroups after 2000 years.
You see, over time, some males have only daughters. Some die before childbearing age because a bear eats them. Etc.
Those lineages die with them.
Put another way: If 10 people decide to populate a small island somewhere, and there are no further invasions, the number of lineages on that island can only go in one direction. It can't go up, barring a freak series of mutations. It can only go down.
The variability will decrease over time. This can (and judging by many posts here - DOES) give the ILLUSION that the original population was smaller than it was.
I repeat: a place that did not have widespread invasions will see the number of its patrilines and matrilines go in one direction only: down. This is true for all isolated places around the globe. If we let a place stay like that until infinity, eventually all people would have the same patriline and matriline, because a certain percentage die out every generation.
Note this is different from saying they will all be related. They can keep genetic variability to some extent, but patrilines are a binary equation: each generation, they die or have male offspring.
A locale having a large percentage of one patrilines can deceive people to thinking that that only one group of guys was having kids, because they were "royalty" or had "harems."
There is no place on the globe, not even in the case of Genghis Khan, where one royal line, family, or clan has direct offspring in the present that total more than 10% in certain regions.
This is scientific and mathematical fact. I don't know how more plainly to state it. Please let me know if anything is unclear.