I previously posted about ‘cousin marriage’ and ‘pedigree collapse’ in my tree here.
I had wondered what effect two less ancestors would have on the ancestor count in my family tree. It turned out, two less ancestors meant that in 17 generations I had 254 less ancestors.
I’ve now discovered another cousin marriage in my tree.
My 4th great-grandparents, Arthur Buchan and Agnes Buchan, married at Rathen, Aberdeenshire in 1828. Their fathers were brothers (as shown in the diagram below).
My pedigree is now only typical until the 8th generation, where I lose two 5x great grandparents, which leads to the loss of another 2046 ancestors by the 17th generation.
My ancestor count now looks like this:
| Generation | Relationship | Typical Number | My Number | Ancestors Lost |
| 1 | Me | |||
| 2 | Parents | 2 | 2 | |
| 3 | Grandparents | 4 | 4 | |
| 4 | 1x Great grandparents | 8 | 8 | |
| 5 | 2x Great grandparents | 16 | 16 | |
| 6 | 3x Great grandparents | 32 | 32 | |
| 7 | 4x Great grandparents | 64 | 64 | |
| 8 | 5x Great grandparents | 128 | 126 | -2 |
| 9 | 6x Great grandparents | 256 | 252 | -4 |
| 10 | 7x Great grandparents | 512 | 504 | -8 |
| 11 | 8x Great grandparents | 1024 | 1006 | -16-2 |
| 12 | 9x Great grandparents | 2048 | 2012 | -32-4 |
| 13 | 10x Great grandparents | 4096 | 4024 | -64-8 |
| 14 | 11x Great grandparents | 8192 | 8048 | -128-16 |
| 15 | 12x Great grandparents | 16384 | 16096 | -256-32 |
| 16 | 13x Great grandparents | 32768 | 31562 | -512-64 |
| 17 | 14x Great grandparents | 65536 | 64384 | -1024-128 |
| TOTAL | 131070 | 128770 | -2300 |
If I find any more, I will make sure to update.
(If you believe that I have actually calculated incorrectly, please let me know!)
