How many great grandparents were born ten generations ago?

The answer is 8

* 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 * 256 Great Great Great Great Great Great Grandparents * 512 Great Great Great Great Great Great Great Grandparents * 1024 Great Great Great Great Great Great Great Great Grandparents