How many great great grandparents does everyone have?

Answer 1

If there have been no marriages between cousins, a person will have:

4 grandparents

8 g-grandparents

16 gg-grandparents

32 ggg-granparents

64 gggg-grandparents

128 ggggg-grandparents

Answer 2

You might think you just multiply everything by 2:

2 parents

4 grandparents

8 great grandparents

16 great great grandparents

32 great great great grandparents

64 great great great great grandparents

128 great great great great great grandparents

but you would be wrong. If you went back like this, the population required 50 generations ago would be over a million billions! The current world population is less than seven billion.

The crucial factor is inter-breeding, of course.

In the extreme case of incest between a brother and a sister (if you will forgive the purely mathematical consideration), any offspring would have only two grandparents. In the rather more common case of first cousins breeding, there will be only six great grandparents to the offspring (each cousin having one pair of grand parents in common and one pair unique, who become great grandparents to their offspring).

The further back you go, the more likely, and also the more complex, are the effects of this inter breeding. Remember, communities tended to be much more geographically restricted in the past.

So, the quick answer is....well, it depends on the mobility of the ancestors, but 30 as an average, perhaps? A pure guess, I'm afraid, but certainly less than the 64 predicted above.

Answer 3

Except for those who have marriages between cousins in their family background, everyone has 8 sets of great great grandparents, for a total of 16 people. (Each generation back doubles the number of ancestors; 1 self, 2 parents, 4 grandparents, 8 great grandparents, so 16 great great grandparents.)

Answer 4

Uh...... 475823475349572349573495?