Thank you for the thoughtful response. However, I know this.
Look what I say here:
And
here.
When I say two populations were isolated from each other prior to colonization, I am not saying those were two static, unchanging populations for millennia. I am saying you need to go a long ways back to find common ancestors.
Migration, intermixing, and diversity are essential parts of the human story. I have written about this several times on CFC, usually to some fanfare. However, it seems that once I fail to repeat that point over and over again, people become extremely suspicious of what I'm saying.
This was interesting, thanks.
ok
When I say two populations were isolated from each other prior to colonization, I am not saying those were two static, unchanging populations for millennia. I am saying you need to go a long ways back to find common ancestors.
Regarding that common ancestor:
Do mind here the effect of the asymetry between males and females survival after tribal conquests.
If you look at the mt-DNA Haplogroup maps across Europe (that Eupedia link) you see them much more evenly spread over Europe than the male Y-DNA haplogroups....
If you combine that with for example the period 6,000-2,000 BC where male Y-DNA diversity goes down (implying wars killing males), you combine that with the typical Celtic-Germanic chieftain nobility culture with polygamy...
And tribes warring and roaming through Europe, killing most male, making offspring with conquered females (at probable higher fertility/lower mortality rate from better food-status etc)...
You end up with tribes that all the time mix almost completely (!) with all the conquered tribes (except for that one Y-DNA chromosome of the 23 in total).
=> those tribes... those "populations... were continuously mixed (with 22 chromosomes) with all other populations as long as there were wars from expansion or wandering between populations.
now... mixing does not mean that the populations were for those 22 chromosomes the same between north and south Europe.
Three helpfull ways to look at that are the tolerance for lactose (milk was an important protein source in more Northern Europe and BTW Basque area), look at skin color (because of the need for Vit D, important for more elastic pelvis for lower maternal mortality), and look at plant poison food tolerances.
These factors make a difference in survival-mortality and fertility rate, and were able to adapt the population to the geographic area by reducing people with unfit genes regarding lactose, Vit D, food allergies.
To put that to a more extreme example:
* Tribe A invades in 5,000 BC a more Northern area with ofc less sun (needing a lighter skin for enough Vit D), with milk as normal protein food (lactose), with other crops (food allergies).
* Tribe B is conquered and for sake of simplicity all male killed, and the female become wifes of Tribe A males. 1 male + 2 wifes (one of A, one of B) => one-third of (the genes) of Tribe A is now Tribe B, except the Y-DNA (0%) and the mt-DNA (50%)
* Give that some generations time with all the time the offspring having those 22 chromosomes of the victorious Tribe B have a higher mortality rate, produce less offspring with B chromosomes.
* Too lazy to do the math, but I guess they could very well blend 50/50 in a reasonable fast period.
* rinse and repeat with the next war and victory of Tribe "A". Or should I say Tribe AB ?
=> not so much adaptation to the environment by new mutations, but more a removing of genes that do not fit to the environment after a quick start by picking up the usefull genes for that environment from existing tribes.
With a Northern tribe going south I guess the mixing would take more time. But IDK. In the South you need more protection against the sun, again other food allergies, other insects and diseases....
(The same could have happened BTW when Homo Sapiens moved out of Africa (a big hurdle) and was in need of some Neanderthaler genes to get the food tolerances for the different plants in Europe (compared to Africa). They needed some crossbreeding first, followed by a period of optimising, before really moving on into EuroAsia).
As main conclusion:
The common male ancestor of the colonists 500 years ago could very well be many thousands years ago. But the common female ancestor much more recent.
And from there: the bulk of the genes (of those 22 chromosomes) except for some genes filtered out by the local environment... the bulk of the genes of colonists were already highly and "recently" mixed.
Whereby noted that this high speed mixing process stopped with Christianity and monogamy, spreading from South Europe to more Northern Europe, and normal intermingling took over (at a much lower rate because the period of wandering tribes was over incl polygamy)