Randomness, Nr 1?

Question

What are the chances of me discovering that the girl I fancy is a blood relative from nearly 2000 years ago?

Answer 1

Great question, Cuz!

Short answer:    Almost 100 percent

Using a non-genetic model, the Most Recent Common Ancestor* of all living human beings may have lived between the 3rd millennium BCE to the first millennium CE.  In one set of estimates, the mean time back to a universal ancestor is 2,300 years, or 76 generations of 30 years each--the time of Aristotle and the pyramids. Thus, everyone in the world today is descended from the Egyptian royal house (ca. 1600 BCE) and Confucius (500 BCE).  That means that statistically, at least, every Muslim, Jew, and Westerner is a descendant of Muhammad (CE 600).

For some populations, the time period to the MRCA is much shorter.  For example, everyone of European descent alive today descends from Charlemagne; or to be more accurate, about 80 percent of the people in Europe living in Charlemagne's time--whatever their social class--are also the ancestors of everyone in the West.  Indeed, one genealogist theorizes that the MRCA of every European alive today was someone who lived in the more recent past--600 years ago, or say around CE 1400.  I would put the time around 1350, the time the Black Death, or the Bubonic Plague, reached Europe.  

Of course, documenting this descent from a MRCA is another matter.

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* Most recent common ancestor is commonly abbreviated MRCA.

Answer 2

If you can get back 2000 years, then you are a "better" genealogy than a lot of people.  Genealogy involves documentation of all of the  generations and documentation gets scant in many places after you go back only a couple of years.  However, that being said, if everyone was able to go back 2000 years with certainty, I think you would be suprised how many people you are actually related to- especially if your ancestors and your ancestors are from the same places.  Think about it... for each generation you go back, your number of ancestors double because everyone has two parents, 4 grandparents, 8 g grandparents, 16, g g grandparents, 32 gr gr gr grandparents, 64 gr gr gr gr grandparents, etc.  You can see that the  numbers multiply quickly.

Answer 3

Here is something for you to figure out.

The world population in AD 1 is estimated at 231 million.

The population of the world today is estimated at  6.7 billion.

What do you think are the odds that you are related to your next door neighbour ? Or the people across the street ? Or the people in the queue at MacDonalds ? As well as the girl that you fancy.