This is a copy of a post I made earlier this year on the late lamented Scotlandspeople discussion group, which offers one reason for trying to go back as far as possible.
It's been said that all those with Scottish ancestry are descended from King Malcolm Canmore ("big head") III (1031-1093); that all with English ancestry are descendants of King Edward I of England (1272-1307), and that all with the slightest trace of European blood in them are the descendants of the Emperor Charlemagne (742-814).
I'd bet we all would like to find some aristocratic ancestor, irrespective of our attitudes to the aristocracy and our political opinions - it is after all, the only way to get further back than the 16th century.
A Danish neighbour recently showed me her family genealogy (privately-published - with heavy wooden bindings - in the 1950's), tracing her family back to Danish medieval royalty, something she was understandably proud of, perhaps especially as her family in recent generations has been smallholders and factory workers. I unfortunately offered the opinion that such royal ancestry was probably more common than we often imagine. The lady was not amused!
This led me to some arithmetical speculation.
Assume an average 30-year generation (women giving birth between the ages of 20 and 40). The earliest records of the aristocracy seem to be around the 8th century, 13 centuries ago. That's about 40 generations. 2 to the power 40 is over one million million (i.e a British billion, if anyone still uses them) ancestors. Certainly a lot more than the 6 thousand million alive today - or then, of course!
Let's assume of the sake of simplicitity that all a given individual's ancestors came from Scotland. I haven't been able to find population estimates for Scotland in the Dark Ages, though the population of Roman Britain in the 4th century is estimated to have been 1.5 million.
Say 100,000, and assume for the sake of argument they all had descendants. Then on average, each person alive then would appear 11 million times each on our modern genealogist's family tree. Some more, some less, but not even rigid social structures could prevent any individual alive then from eventually contributing to the ancestry of everyone in that country. Only complete geographical isolation could have done that, and in the Dark Ages some people travelled a lot more than is often imagined - eg. Vikings travelled to Central Asia where they traded with Arabs, Africans and Chinese.
So we really are all related, and at a much more recent date than the clan mothers and fathers suggested by DNA research (which can only trace direct maternal and paternal lines). And the numbers involved indicate the limits of genealogy - we're probably lucky that the church records don't go further back than 1550!
However, there's not much point in it if you can't prove the link and find that slender branch or two that suddenly opens up to reveal countless and lengthy well-documentend branches of the nobility. So what are the chances? Let's assume all Scottish church records went back to 1550 (no, don't laugh - we're assuming 'best case') That's 15 generations, i.e there are 32768 ancestors at that level. I'm guessing the population of Scotland at the time was around 500,000, so those ancestors constituted 6% of the population - at best: even here, the same people probably will turn up in different branches, what with people marrying 'double cousins' and the like.
What percentage of the population were aristocrats (i.e. those who recorded their ancestry)? 0.5% is a pure guess - so 2500 aristocrats out of 500,000. Pick an individual living in 1550 at random, and do this 32768 times, corresponding to your ancestors 15 generations ago.
We can say at random, since we're assuming we know nothing so far about those ancestors.
The probability that any given individual in Scotland in 1550 is an aristocrat is 2500/500000 i.e the probability that the individual is not is 497500/500000. The probability that none of the 32768 'random' individuals are aristocrats is 497500/500000 multiplied by itself 32768 times.
(actually you should subtract one from the 500000 each time, since that indivudual is no longer 'in the running', but lets keep it simple).
497500/500000 to the power 32768, a very small number indeed. Even if we took only 1000 ancestors, the chance of none of them being an aristocrat is under 1% (again, assuming the 'randomness' provided by having no knowledge of these ancestors - you can't just pick 1000 more recent ancestors and assume the same, since you presumably know more about them). The chance of an aristocrat being among the 32768 is therefore extremely close to 100%.
So not only is is absolutely certain that all of us here researching our Scottish ancestry are descendants of medieval royalty (and everyone else who lived then), but there is a very high chance of finding an aristocratic branch leading back before 1550 if only you can follow most of your ancestry back 15 generations using the Old Parish Records.
